diff --git a/CHANGELOG.md b/CHANGELOG.md
index 640a2b893..d89441b0a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,8 +4,9 @@
 
 ### Added
 
-- relay: add infos "relay_api_version" and "relay_api_version_number"
+- relay: add option relay.network.websocket_permessage_deflate
 - relay: add option relay.look.raw_messages_max_length ([#2122](https://github.com/weechat/weechat/issues/2122))
+- relay: add infos "relay_api_version" and "relay_api_version_number"
 
 ### Fixed
 
diff --git a/po/cs.po b/po/cs.po
index b7f7328aa..539409b5b 100644
--- a/po/cs.po
+++ b/po/cs.po
@@ -21,7 +21,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Ondřej Súkup <mimi.vx@gmail.com>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -14600,6 +14600,16 @@ msgid ""
 "\"^https?://(www\\.)?example\\.(com|org)\""
 msgstr ""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 #, fuzzy
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
diff --git a/po/de.po b/po/de.po
index 77b682617..9bc58fc43 100644
--- a/po/de.po
+++ b/po/de.po
@@ -26,7 +26,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-05-31 20:32+0200\n"
 "Last-Translator: Nils Görs <weechatter@arcor.de>\n"
 "Language-Team: German <kde-i18n-de@kde.org>\n"
@@ -2108,11 +2108,11 @@ msgstr ""
 "undOperatoren (+, -, *, /, //, %, **)"
 
 msgid ""
-"  - ${random:min,max}: a random integer number between \"min\" and "
-"\"max\" (inclusive)"
+"  - ${random:min,max}: a random integer number between \"min\" and \"max\" "
+"(inclusive)"
 msgstr ""
-"  - ${random:min,max}: eine zufällige ganze Zahl zwischen \"min\" "
-"und\"max\" (einschließlich)"
+"  - ${random:min,max}: eine zufällige ganze Zahl zwischen \"min\" und\"max\" "
+"(einschließlich)"
 
 msgid "  - ${translate:string}: the translated string"
 msgstr "  - ${translate:string}: die übersetzte Zeichenkette"
@@ -3043,8 +3043,8 @@ msgid ""
 "  raw[chat(xxx)]: chat area for buffer with name \"xxx\" (full name "
 "including plugin)"
 msgstr ""
-"  raw[chat(xxx)]: Chatbereich für einen Buffer mit dem Namen "
-"\"xxx\" (vollständiger Name, mit Erweiterung)"
+"  raw[chat(xxx)]: Chatbereich für einen Buffer mit dem Namen \"xxx\" "
+"(vollständiger Name, mit Erweiterung)"
 
 msgid "  raw[bar(*)]: any bar"
 msgstr "  raw[bar(*)]: beliebige Bar"
@@ -4984,8 +4984,8 @@ msgstr ""
 "\"-yes\" ausgeführt werden (siehe /help quit)"
 
 msgid ""
-"if set, /upgrade command must be confirmed with extra argument \"-"
-"yes\" (see /help upgrade)"
+"if set, /upgrade command must be confirmed with extra argument \"-yes\" "
+"(see /help upgrade)"
 msgstr ""
 "ist diese Einstellung aktiviert, muss der \"/upgrade\" Befehl mit dem "
 "Argument \"-yes\" ausgeführt werden (siehe /help upgrade)"
@@ -5041,10 +5041,10 @@ msgid ""
 "weechat.color.emphasized* are used"
 msgstr ""
 "Attribute um Textpassagen hervorzuheben: Das setzen von ein- oder mehreren "
-"Attributen ist möglich (\"%\" für blinkenden Text, \".\" zum "
-"\"dimmen\" (halbe Helligkeit),\"*\" für fett, \"!\" für invertiert, \"/\" "
-"für kursiv, \"_\" für unterstrichen); wenn die Zeichenkette leer ist, werden "
-"die Farben genutzt die durch weechat.color.emphasized* definiert sind"
+"Attributen ist möglich (\"%\" für blinkenden Text, \".\" zum \"dimmen\" "
+"(halbe Helligkeit),\"*\" für fett, \"!\" für invertiert, \"/\" für kursiv, "
+"\"_\" für unterstrichen); wenn die Zeichenkette leer ist, werden die Farben "
+"genutzt die durch weechat.color.emphasized* definiert sind"
 
 msgid ""
 "comma separated list of words to highlight; case insensitive comparison (use "
@@ -7017,24 +7017,24 @@ msgstr ""
 "Bedingungen um eine Infobar anzuzeigen. Eine einfache Bedingung: \"active\", "
 "\"inactive\", \"nicklist\" (Fenster muss aktiv/inaktiv sein oder der Buffer "
 "enthält eine Benutzerliste), oder man nutzt einen Ausdruck mit Bedingungen "
-"(siehe /help eval). Beispiele: \"${nicklist} && ${info:term_width} > "
-"100\" (lokale Variablen für den Ausdruck sind ${active}, ${inactive} und "
+"(siehe /help eval). Beispiele: \"${nicklist} && ${info:term_width} > 100\" "
+"(lokale Variablen für den Ausdruck sind ${active}, ${inactive} und "
 "${nicklist})"
 
 msgid "bar position (bottom, top, left, right)"
 msgstr "Position der Infobar (unten, oben, links, rechts)"
 
 msgid ""
-"bar filling direction (\"horizontal\" (from left to right) or "
-"\"vertical\" (from top to bottom)) when bar position is top or bottom"
+"bar filling direction (\"horizontal\" (from left to right) or \"vertical\" "
+"(from top to bottom)) when bar position is top or bottom"
 msgstr ""
 "Darstellung innerhalb der Infobar, falls die Infobar oben/unten angezeigt "
 "wird (\"horizontal\" (von links nach rechts) oder \"vertikal\" (von oben "
 "nach unten))"
 
 msgid ""
-"bar filling direction (\"horizontal\" (from left to right) or "
-"\"vertical\" (from top to bottom)) when bar position is left or right"
+"bar filling direction (\"horizontal\" (from left to right) or \"vertical\" "
+"(from top to bottom)) when bar position is left or right"
 msgstr ""
 "Darstellung innerhalb der Infobar, falls die Infobar links/rechts angezeigt "
 "wird (\"horizontal\" (von links nach rechts) oder \"vertikal\" (von oben "
@@ -7074,9 +7074,9 @@ msgid "separator line between bar and other bars/windows"
 msgstr "Trennzeichen zwischen verschieden Infobars und Fenstern"
 
 msgid ""
-"items of bar, they can be separated by comma (space between items) or \"+"
-"\" (glued items); special syntax \"@buffer:item\" can be used to force "
-"buffer used when displaying the bar item"
+"items of bar, they can be separated by comma (space between items) or \"+\" "
+"(glued items); special syntax \"@buffer:item\" can be used to force buffer "
+"used when displaying the bar item"
 msgstr ""
 "Items einer Bar können entweder durch Kommata (\",\") voneinander getrennt "
 "(setzt ein Leerzeichen zwischen die Items), oder durch ein \"+\" Zeichen "
@@ -8820,8 +8820,8 @@ msgid "    - ${description}: option description (translated)"
 msgstr "    - ${description}: Beschreibung der Option (übersetzt)"
 
 msgid ""
-"    - ${description2}: option description (translated), \"(no "
-"description)\" (translated) if there's no description"
+"    - ${description2}: option description (translated), \"(no description)\" "
+"(translated) if there's no description"
 msgstr ""
 "    - ${description2}: Beschreibung der Option (übersetzt), \"(keine "
 "Beschreibung)\" (übersetzt) falls keine Beschreibung vorhanden"
@@ -9512,8 +9512,8 @@ msgstr ""
 
 #, c-format
 msgid ""
-"%s%s: if you want to add a standard server, use the command \"/server "
-"add\" (see /help server); if you really want to add a temporary server (NOT "
+"%s%s: if you want to add a standard server, use the command \"/server add\" "
+"(see /help server); if you really want to add a temporary server (NOT "
 "SAVED), turn on the option irc.look.temporary_servers"
 msgstr ""
 "%s%s: falls ein Standardserver erstellt werden soll, muss der Befehl \"/"
@@ -12676,8 +12676,8 @@ msgid ""
 "interval between two checks for notify with IRC command \"whois\" (in "
 "minutes)"
 msgstr ""
-"Intervall zwischen zwei notify Überprüfungen mit dem IRC Befehl "
-"\"whois\" (in Minuten)"
+"Intervall zwischen zwei notify Überprüfungen mit dem IRC Befehl \"whois\" "
+"(in Minuten)"
 
 msgid ""
 "cause SASL authentication failure when SASL is requested but unavailable on "
@@ -15025,19 +15025,19 @@ msgstr "%s%s: Interpreter kann nicht freigeben werden"
 
 #, c-format
 msgid ""
-"%s%s: too few arguments received from client %s%s%s for resource "
-"\"%s\" (received: %d arguments, expected: at least %d)"
+"%s%s: too few arguments received from client %s%s%s for resource \"%s\" "
+"(received: %d arguments, expected: at least %d)"
 msgstr ""
 "%s%s: Zu wenige Argumente von Client %s%s%s für die Ressource \"%s\" "
 "erhalten (Empfangen: %d Argumente, mindestens erwartet: %d)"
 
 #, c-format
 msgid ""
-"%s%s: too many arguments received from client %s%s%s for resource "
-"\"%s\" (received: %d arguments, expected: at most %d)"
+"%s%s: too many arguments received from client %s%s%s for resource \"%s\" "
+"(received: %d arguments, expected: at most %d)"
 msgstr ""
-"%s%s: Zu viele Argumente von Client erhalten %s%s%s für die Ressource "
-"\"%s\" (Empfangen: %d Argumente, höchstens erwartet: %d)"
+"%s%s: Zu viele Argumente von Client erhalten %s%s%s für die Ressource \"%s\" "
+"(Empfangen: %d Argumente, höchstens erwartet: %d)"
 
 #, c-format
 msgid "%s%s: failed to execute route \"%s %s\" for client %s%s%s"
@@ -16036,6 +16036,16 @@ msgstr ""
 "unterscheiden kann \"(?-i)\" vorangestellt werden), Beispiel: ^https?://"
 "(www\\.)?example\\.(com|org)\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
@@ -16144,8 +16154,8 @@ msgid ""
 "%s%s: error: file with TLS certificate/key is not readable: \"%s\" (option "
 "relay.network.tls_cert_key)"
 msgstr ""
-"%s%s: Fehler: Datei mit TLS Zertifikat/Schlüssel ist nicht lesbar: "
-"\"%s\" (Option relay.network.tls_cert_key)"
+"%s%s: Fehler: Datei mit TLS Zertifikat/Schlüssel ist nicht lesbar: \"%s\" "
+"(Option relay.network.tls_cert_key)"
 
 #, c-format
 msgid "%s%s: unable to initialize priority for TLS"
@@ -16289,8 +16299,8 @@ msgstr ""
 
 #, c-format
 msgid ""
-"%s%s: too few arguments received from client %s%s%s for command "
-"\"%s\" (received: %d arguments, expected: at least %d)"
+"%s%s: too few arguments received from client %s%s%s for command \"%s\" "
+"(received: %d arguments, expected: at least %d)"
 msgstr ""
 "%s%s: Zu wenige Argumente von Client %s%s%s für den Befehl \"%s\" erhalten "
 "(Empfangen: %d Argumente, mindestens Erwartet: %d)"
@@ -17459,22 +17469,22 @@ msgstr "verwaltet Trigger, das Schweizer Armeemesser für WeeChat"
 #. TRANSLATORS: only text between angle brackets (eg: "<name>") must be translated
 msgid ""
 "list [-o|-ol|-i|-il] || listfull || listdefault || add|addoff|addreplace "
-"<name> <hook> "
-"[\"<arguments>\" [\"<conditions>\" [\"<regex>\" [\"<command>\" [\"<return_code>\" [\"<post_action>\"]]]]]] "
-"|| addinput [<hook>] || input|output|recreate <name> || set <name> <option> "
-"<value> || rename|copy <name> <new_name> || enable|disable|toggle [<name>|"
-"<mask> [<name>|<mask>...]] || restart <name>|<mask> [<name>|<mask>...] || "
-"show <name> || del <name>|<mask> [<name>|<mask>...] || restore <name>|<mask> "
-"[<name>|<mask>...] || default -yes || monitor [<filter>]"
+"<name> <hook> [\"<arguments>\" [\"<conditions>\" [\"<regex>\" [\"<command>\" "
+"[\"<return_code>\" [\"<post_action>\"]]]]]] || addinput [<hook>] || input|"
+"output|recreate <name> || set <name> <option> <value> || rename|copy <name> "
+"<new_name> || enable|disable|toggle [<name>|<mask> [<name>|<mask>...]] || "
+"restart <name>|<mask> [<name>|<mask>...] || show <name> || del <name>|<mask> "
+"[<name>|<mask>...] || restore <name>|<mask> [<name>|<mask>...] || default -"
+"yes || monitor [<filter>]"
 msgstr ""
 "list [-o|-ol|-i|-il] || listfull || listdefault || add|addoff|addreplace "
-"<name> <hook> "
-"[\"<arguments>\" [\"<conditions>\" [\"<regex>\" [\"<command>\" [\"<return_code>\" [\"<post_action>\"]]]]]] "
-"|| addinput [<hook>] || input|output|recreate <name> || set <name> <option> "
-"<value> || rename|copy <name> <new_name> || enable|disable|toggle [<name>|"
-"<mask> [<name>|<mask>...]] || restart <name>|<mask> [<name>|<mask>...] || "
-"show <name> || del <name>|<mask> [<name>|<mask>...] || restore <name>|<mask> "
-"[<name>|<mask>...] || default -yes || monitor [<filter>]"
+"<name> <hook> [\"<arguments>\" [\"<conditions>\" [\"<regex>\" [\"<command>\" "
+"[\"<return_code>\" [\"<post_action>\"]]]]]] || addinput [<hook>] || input|"
+"output|recreate <name> || set <name> <option> <value> || rename|copy <name> "
+"<new_name> || enable|disable|toggle [<name>|<mask> [<name>|<mask>...]] || "
+"restart <name>|<mask> [<name>|<mask>...] || show <name> || del <name>|<mask> "
+"[<name>|<mask>...] || restore <name>|<mask> [<name>|<mask>...] || default -"
+"yes || monitor [<filter>]"
 
 msgid "raw[list]: list triggers (without argument, this list is displayed)"
 msgstr ""
diff --git a/po/es.po b/po/es.po
index 4fddd8b4f..4ba377951 100644
--- a/po/es.po
+++ b/po/es.po
@@ -22,7 +22,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Santiago Forero <santiago@forero.xyz>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -14929,6 +14929,16 @@ msgstr ""
 "mapeada a IPv6 (como: \"::ffff:127.0.0.1\"), ejemplo: \"^((::ffff:)?"
 "123\\.45\\.67\\.89|192\\.160\\..*)$\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/fr.po b/po/fr.po
index 9186ccb9e..a8cda2b1a 100644
--- a/po/fr.po
+++ b/po/fr.po
@@ -21,8 +21,8 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
-"PO-Revision-Date: 2024-05-31 12:02+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
+"PO-Revision-Date: 2024-06-01 12:58+0200\n"
 "Last-Translator: Sébastien Helleu <flashcode@flashtux.org>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
 "Language: fr\n"
@@ -15721,6 +15721,24 @@ msgstr ""
 "pour la rendre sensible à la casse), exemple : \"^https?://(www\\.)?"
 "example\\.(com|org)\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+"activer l'extension websocket \"permessage-deflate\" pour compresser les "
+"paquets websocket, avec les protocoles weechat et api ; si désactivé, "
+"WeeChat (en tant que serveur) n'activera pas permessage-deflate même si le "
+"client le supporte, et lors d'une connexion à un WeeChat distant (relai api "
+"seulement), le support permessage-deflate ne sera pas annoncé par WeeChat ; "
+"il est recommandé de garder cette option activée, et vous ne devriez la "
+"désactiver que si vous rencontrez des problèmes avec cette extension, avec "
+"WeeChat ou le client"
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/hu.po b/po/hu.po
index 058765040..4c744bd5a 100644
--- a/po/hu.po
+++ b/po/hu.po
@@ -20,7 +20,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Andras Voroskoi <voroskoi@frugalware.org>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -13971,6 +13971,16 @@ msgid ""
 "\"^https?://(www\\.)?example\\.(com|org)\""
 msgstr ""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 #, fuzzy
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
diff --git a/po/it.po b/po/it.po
index 8853938e2..1a2f97e9b 100644
--- a/po/it.po
+++ b/po/it.po
@@ -20,7 +20,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Esteban I. Ruiz Moreno <exio4.com@gmail.com>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -14969,6 +14969,16 @@ msgstr ""
 "ffff:127.0.0.1\",come: \"::ffff:127.0.0.1\"), esempio: \"^((::ffff:)?"
 "123\\.45\\.67\\.89|192\\.160\\..*)$\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/ja.po b/po/ja.po
index 56d14784d..67c2f7ac0 100644
--- a/po/ja.po
+++ b/po/ja.po
@@ -20,7 +20,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: AYANOKOUZI, Ryuunosuke <i38w7i3@yahoo.co.jp>\n"
 "Language-Team: Japanese <https://github.com/l/weechat/tree/master/"
@@ -15429,6 +15429,16 @@ msgstr ""
 "字を区別しない、\"(?-i)\" を先頭に置くと大文字小文字を区別する)、例: "
 "\"^https?://(www\\.)?example\\.(com|org)\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/pl.po b/po/pl.po
index 4e989448e..3124413b0 100644
--- a/po/pl.po
+++ b/po/pl.po
@@ -22,7 +22,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-05-25 13:34+0200\n"
 "Last-Translator: Krzysztof Korościk <soltys@soltys.info>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -15296,6 +15296,16 @@ msgstr ""
 "początku sprawi, że wielość znaków będzie miała znaczenie), przykład: "
 "\"^http://(www\\.)?przykład\\.(com|org)\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/pt.po b/po/pt.po
index 6ed1fdfe0..e9ec7a531 100644
--- a/po/pt.po
+++ b/po/pt.po
@@ -20,7 +20,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Vasco Almeida <vascomalmeida@sapo.pt>\n"
 "Language-Team: Portuguese <>\n"
@@ -15315,6 +15315,16 @@ msgstr ""
 "(não distingue maiúscula e minúsculas , use \"(?-i)\" no início para "
 "distinguir), exemplo: \"^http://(www\\.)?exemplo\\.(com|org)\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/pt_BR.po b/po/pt_BR.po
index 9635c9a87..112cbea4c 100644
--- a/po/pt_BR.po
+++ b/po/pt_BR.po
@@ -21,7 +21,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Érico Nogueira <ericonr@disroot.org>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -14435,6 +14435,16 @@ msgstr ""
 "expressão regular com IPs permitidos a usar o relay, por exemplo: "
 "\"^(123\\.45\\.67\\.89|192\\.160\\..*)$\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 #, fuzzy
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
diff --git a/po/ru.po b/po/ru.po
index 040f856ec..1c749dfa5 100644
--- a/po/ru.po
+++ b/po/ru.po
@@ -21,7 +21,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Aleksey V Zapparov AKA ixti <ixti@member.fsf.org>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -14024,6 +14024,16 @@ msgid ""
 "\"^https?://(www\\.)?example\\.(com|org)\""
 msgstr ""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 #, fuzzy
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
diff --git a/po/sr.po b/po/sr.po
index 2ca512631..f9307e0b6 100644
--- a/po/sr.po
+++ b/po/sr.po
@@ -20,7 +20,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-05-07 14:00+0400\n"
 "Last-Translator: Ivan Pešić <ivan.pesic@gmail.com>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -15283,6 +15283,16 @@ msgstr ""
 "разлика, употребите „(?-i)” на почетку), пример: „^https?://(www\\.)?"
 "example\\.(com|org)”"
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/tr.po b/po/tr.po
index 45dd9b35f..46d3922dc 100644
--- a/po/tr.po
+++ b/po/tr.po
@@ -20,7 +20,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2024-04-07 14:50+0200\n"
 "Last-Translator: Emir SARI <emir_sari@icloud.com>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -15635,6 +15635,16 @@ msgstr ""
 "(BÜYÜK/küçük harf duyarsız, duyarlı yapmak için başında \"(?-i)\" kullanın, "
 "örnek: \"^https?://(www\\.)?example\\.(com|org)\""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/po/weechat.pot b/po/weechat.pot
index 623d7ed7f..7eb66e683 100644
--- a/po/weechat.pot
+++ b/po/weechat.pot
@@ -21,7 +21,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: WeeChat\n"
 "Report-Msgid-Bugs-To: flashcode@flashtux.org\n"
-"POT-Creation-Date: 2024-05-31 12:01+0200\n"
+"POT-Creation-Date: 2024-06-01 12:54+0200\n"
 "PO-Revision-Date: 2014-08-16 10:27+0200\n"
 "Last-Translator: Sébastien Helleu <flashcode@flashtux.org>\n"
 "Language-Team: weechat-dev <weechat-dev@nongnu.org>\n"
@@ -12784,6 +12784,16 @@ msgid ""
 "\"^https?://(www\\.)?example\\.(com|org)\""
 msgstr ""
 
+msgid ""
+"enable websocket extension \"permessage-deflate\" to compress websocket "
+"frames, with weechat and api protocols; if disabled, WeeChat (as server) "
+"will not enable permessage-deflate even if the client supports it, and when "
+"connecting to a remote WeeChat (api relay only), permessage-deflate support "
+"is not advertised by WeeChat; it is recommended to keep this option enabled, "
+"and you should disable it only if you have troubles with this extension, "
+"either with WeeChat or the client"
+msgstr ""
+
 msgid ""
 "maximum number of minutes in backlog per IRC channel (0 = unlimited, "
 "examples: 1440 = one day, 10080 = one week, 43200 = one month, 525600 = one "
diff --git a/src/plugins/relay/api/remote/relay-remote-network.c b/src/plugins/relay/api/remote/relay-remote-network.c
index 8cb054e2c..7b08530ee 100644
--- a/src/plugins/relay/api/remote/relay-remote-network.c
+++ b/src/plugins/relay/api/remote/relay-remote-network.c
@@ -34,6 +34,7 @@
 #include "../../../weechat-plugin.h"
 #include "../../relay.h"
 #include "../../relay-auth.h"
+#include "../../relay-config.h"
 #include "../../relay-http.h"
 #include "../../relay-raw.h"
 #include "../../relay-remote.h"
@@ -642,7 +643,7 @@ relay_remote_network_connect_ws_auth (struct t_relay_remote *remote)
 {
     char *password, *totp_secret, *totp;
     char *salt_password, salt[64], str_auth[4096], str_auth_base64[4096];
-    char str_http[8192], str_totp[128];
+    char str_http[8192], str_totp[128], str_extensions[256];
     char hash[512 / 8], hash_hexa[((512 / 8) * 2) + 1];
     char ws_key[16], ws_key_base64[64];
     int hash_size;
@@ -654,6 +655,7 @@ relay_remote_network_connect_ws_auth (struct t_relay_remote *remote)
     totp_secret = NULL;
     str_auth[0] = '\0';
     str_totp[0] = '\0';
+    str_extensions[0] = '\0';
 
     password = weechat_string_eval_expression (
         weechat_config_string (remote->options[RELAY_REMOTE_OPTION_PASSWORD]),
@@ -744,6 +746,15 @@ relay_remote_network_connect_ws_auth (struct t_relay_remote *remote)
         }
     }
 
+    /* add supported extensions */
+    if (weechat_config_boolean (relay_config_network_websocket_permessage_deflate))
+    {
+        snprintf (str_extensions, sizeof (str_extensions),
+                  "%s",
+                  "Sec-WebSocket-Extensions: permessage-deflate; "
+                  "client_max_window_bits\r\n");
+    }
+
     snprintf (
         str_http, sizeof (str_http),
         "GET /api HTTP/1.1\r\n"
@@ -753,12 +764,13 @@ relay_remote_network_connect_ws_auth (struct t_relay_remote *remote)
         "Sec-WebSocket-Key: %s\r\n"
         "Connection: Upgrade\r\n"
         "Upgrade: websocket\r\n"
-        "Sec-WebSocket-Extensions: permessage-deflate; client_max_window_bits\r\n"
+        "%s"
         "Host: %s:%d\r\n"
         "\r\n",
         str_auth_base64,
         str_totp,
         ws_key_base64,
+        str_extensions,
         remote->address,
         remote->port);
     relay_remote_network_send (remote, RELAY_MSG_STANDARD,
diff --git a/src/plugins/relay/relay-config.c b/src/plugins/relay/relay-config.c
index 37ac028da..018337191 100644
--- a/src/plugins/relay/relay-config.c
+++ b/src/plugins/relay/relay-config.c
@@ -92,6 +92,7 @@ struct t_config_option *relay_config_network_tls_priorities = NULL;
 struct t_config_option *relay_config_network_totp_secret = NULL;
 struct t_config_option *relay_config_network_totp_window = NULL;
 struct t_config_option *relay_config_network_websocket_allowed_origins = NULL;
+struct t_config_option *relay_config_network_websocket_permessage_deflate = NULL;
 
 /* relay config, irc section */
 
@@ -1754,6 +1755,19 @@ relay_config_init ()
             NULL, NULL, NULL,
             &relay_config_change_network_websocket_allowed_origins, NULL, NULL,
             NULL, NULL, NULL);
+        relay_config_network_websocket_permessage_deflate = weechat_config_new_option (
+            relay_config_file, relay_config_section_network,
+            "websocket_permessage_deflate", "boolean",
+            N_("enable websocket extension \"permessage-deflate\" to compress "
+               "websocket frames, with weechat and api protocols; if disabled, "
+               "WeeChat (as server) will not enable permessage-deflate even if "
+               "the client supports it, and when connecting to a remote WeeChat "
+               "(api relay only), permessage-deflate support is not advertised "
+               "by WeeChat; it is recommended to keep this option enabled, "
+               "and you should disable it only if you have troubles with this "
+               "extension, either with WeeChat or the client"),
+            NULL, 0, 100, "on", NULL, 0,
+            NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL);
     }
 
     /* section irc */
diff --git a/src/plugins/relay/relay-config.h b/src/plugins/relay/relay-config.h
index 507724cf4..4dcfd3792 100644
--- a/src/plugins/relay/relay-config.h
+++ b/src/plugins/relay/relay-config.h
@@ -61,6 +61,7 @@ extern struct t_config_option *relay_config_network_tls_priorities;
 extern struct t_config_option *relay_config_network_totp_secret;
 extern struct t_config_option *relay_config_network_totp_window;
 extern struct t_config_option *relay_config_network_websocket_allowed_origins;
+extern struct t_config_option *relay_config_network_websocket_permessage_deflate;
 
 extern struct t_config_option *relay_config_irc_backlog_max_minutes;
 extern struct t_config_option *relay_config_irc_backlog_max_number;
diff --git a/src/plugins/relay/relay-websocket.c b/src/plugins/relay/relay-websocket.c
index 7da984adb..15f228afa 100644
--- a/src/plugins/relay/relay-websocket.c
+++ b/src/plugins/relay/relay-websocket.c
@@ -315,7 +315,7 @@ relay_websocket_parse_extensions (const char *extensions,
         params = weechat_string_split (exts[i], ";", " ", 0, 0, &num_params);
         if (params && (num_params >= 1)
             && (strcmp (params[0], "permessage-deflate") == 0)
-            && (weechat_config_integer (relay_config_network_compression) > 0))
+            && (weechat_config_boolean (relay_config_network_websocket_permessage_deflate)))
         {
             ws_deflate->enabled = 1;
             ws_deflate->server_context_takeover = 1;