diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9c673067b..ee65452bc 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -20,13 +20,15 @@ NOTE: Add new changes BELOW THIS COMMENT.
 
 ### Added
 
+- New property `"language"` in `POST /control/install/check_config` and `POST /control/install/configure` HTTP APIs.
+
 - The user is able to remove the static lease's hostname via the HTTP API.
 
 ### Fixed
 
 - Blocked requests without an EDNS(0) OPT record ([#8183]).
 
-[#8183]:     https://github.com/AdguardTeam/AdGuardHome/issues/8183
+[#8183]: https://github.com/AdguardTeam/AdGuardHome/issues/8183
 
 <!--
 NOTE: Add new changes ABOVE THIS COMMENT.
diff --git a/internal/home/controlinstall.go b/internal/home/controlinstall.go
index 4e26c4bcf..c217ea3f9 100644
--- a/internal/home/controlinstall.go
+++ b/internal/home/controlinstall.go
@@ -84,9 +84,12 @@ type checkConfReqEnt struct {
 }
 
 type checkConfReq struct {
-	Web         checkConfReqEnt `json:"web"`
-	DNS         checkConfReqEnt `json:"dns"`
-	SetStaticIP bool            `json:"set_static_ip"`
+	Web checkConfReqEnt `json:"web"`
+	DNS checkConfReqEnt `json:"dns"`
+
+	Language string `json:"language"`
+
+	SetStaticIP bool `json:"set_static_ip"`
 }
 
 type checkConfRespEnt struct {
@@ -102,8 +105,9 @@ type staticIPJSON struct {
 
 type checkConfResp struct {
 	StaticIP staticIPJSON     `json:"static_ip"`
-	Web      checkConfRespEnt `json:"web"`
 	DNS      checkConfRespEnt `json:"dns"`
+	Language checkConfRespEnt `json:"language"`
+	Web      checkConfRespEnt `json:"web"`
 }
 
 // validateWeb returns error is the web part if the initial configuration can't
@@ -200,6 +204,12 @@ func (web *webAPI) handleInstallCheckConfig(w http.ResponseWriter, r *http.Reque
 	}
 
 	resp := &checkConfResp{}
+
+	err = validateLang(req.Language, true)
+	if err != nil {
+		resp.Language.Status = err.Error()
+	}
+
 	tcpPorts := aghalg.UniqChecker[tcpPort]{}
 	if err = req.validateWeb(tcpPorts); err != nil {
 		resp.Web.Status = err.Error()
@@ -362,19 +372,21 @@ type applyConfigReqEnt struct {
 }
 
 type applyConfigReq struct {
-	Username string `json:"username"`
+	Language string `json:"language"`
 	Password string `json:"password"`
+	Username string `json:"username"`
 
 	Web applyConfigReqEnt `json:"web"`
 	DNS applyConfigReqEnt `json:"dns"`
 }
 
 // copyInstallSettings copies the installation parameters between two
-// configuration structures.
+// configuration structures.  All arguments must not be nil.
 func copyInstallSettings(dst, src *configuration) {
-	dst.HTTPConfig = src.HTTPConfig
 	dst.DNS.BindHosts = src.DNS.BindHosts
 	dst.DNS.Port = src.DNS.Port
+	dst.HTTPConfig = src.HTTPConfig
+	dst.Language = src.Language
 }
 
 // shutdownTimeout is the timeout for shutting HTTP server down operation.
@@ -491,6 +503,10 @@ func (web *webAPI) finalizeInstall(
 		}
 	}()
 
+	if req.Language != "" {
+		config.Language = req.Language
+	}
+
 	config.DNS.BindHosts = []netip.Addr{req.DNS.IP}
 	config.DNS.Port = req.DNS.Port
 	config.Filtering.Logger = web.baseLogger.With(slogutil.KeyPrefix, "filtering")
@@ -589,6 +605,12 @@ func decodeApplyConfigReq(r io.Reader) (req *applyConfigReq, restartHTTP bool, e
 		return nil, false, fmt.Errorf("parsing request: %w", err)
 	}
 
+	err = validateLang(req.Language, true)
+	if err != nil {
+		// Don't wrap the error, because it's informative enough as is.
+		return nil, false, err
+	}
+
 	if req.Web.Port == 0 || req.DNS.Port == 0 {
 		return nil, false, errors.Error("ports cannot be 0")
 	}
diff --git a/internal/home/i18n.go b/internal/home/i18n.go
index b784f0065..4d733cead 100644
--- a/internal/home/i18n.go
+++ b/internal/home/i18n.go
@@ -2,6 +2,7 @@ package home
 
 import (
 	"encoding/json"
+	"fmt"
 	"net/http"
 
 	"github.com/AdguardTeam/AdGuardHome/internal/aghhttp"
@@ -48,6 +49,20 @@ var allowedLanguages = container.NewMapSet(
 	"zh-tw",
 )
 
+// validateLang returns a standard error about if lang is an unknown language.
+// If allowEmpty is true, the language can also be empty.
+func validateLang(lang string, allowEmpty bool) (err error) {
+	if allowEmpty && lang == "" {
+		return nil
+	}
+
+	if !allowedLanguages.Has(lang) {
+		return fmt.Errorf("unknown language: %q", lang)
+	}
+
+	return nil
+}
+
 // languageJSON is the JSON structure for language requests and responses.
 type languageJSON struct {
 	Language string `json:"language"`
@@ -89,8 +104,9 @@ func (web *webAPI) handleI18nChangeLanguage(w http.ResponseWriter, r *http.Reque
 	}
 
 	lang := langReq.Language
-	if !allowedLanguages.Has(lang) {
-		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "unknown language: %q", lang)
+	err = validateLang(lang, false)
+	if err != nil {
+		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
diff --git a/internal/home/profilehttp.go b/internal/home/profilehttp.go
index 73c24e223..1b27f5ce8 100644
--- a/internal/home/profilehttp.go
+++ b/internal/home/profilehttp.go
@@ -94,8 +94,9 @@ func (web *webAPI) handlePutProfile(w http.ResponseWriter, r *http.Request) {
 	}
 
 	lang := profileReq.Language
-	if !allowedLanguages.Has(lang) {
-		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "unknown language: %q", lang)
+	err = validateLang(lang, false)
+	if err != nil {
+		aghhttp.ErrorAndLog(ctx, l, r, w, http.StatusBadRequest, "%s", err)
 
 		return
 	}
diff --git a/openapi/CHANGELOG.md b/openapi/CHANGELOG.md
index 1009cba05..e33f21ccc 100644
--- a/openapi/CHANGELOG.md
+++ b/openapi/CHANGELOG.md
@@ -2,9 +2,13 @@
 
 <!-- TODO(a.garipov): Reformat in accordance with the KeepAChangelog spec. -->
 
-## v0.107.78: API changes
+## v0.107.79: API changes
 
-### New `interval` values in `GET /control/filtering/status` and `POST /control/filtering/config` APIs
+### Setting the UI language through the install API
+
+- New property `"language"` in `POST /control/install/check_config` and `POST /control/install/configure` HTTP APIs defines the language to use once AdGuard Home is installed.
+
+## v0.107.78: API changes
 
 The property `interval` of the objects returned from and accepted by the aforementioned APIs can now be any integer between 0 and 8760 (365 days).
 
diff --git a/openapi/openapi.yaml b/openapi/openapi.yaml
index c214be1cd..c190efbd0 100644
--- a/openapi/openapi.yaml
+++ b/openapi/openapi.yaml
@@ -1,4 +1,4 @@
-'openapi': '3.0.3'
+'openapi': '3.2.0'
 'info':
   'title': 'AdGuard Home'
   'description': >
@@ -1543,8 +1543,7 @@
           'type': 'string'
           'example': 'v0.123.4'
         'language':
-          'type': 'string'
-          'example': 'en'
+          '$ref': '#/components/schemas/Lang'
         'start_time':
           'type': 'number'
           'format': 'double'
@@ -2685,7 +2684,7 @@
         'name':
           'type': 'string'
         'language':
-          'type': 'string'
+          '$ref': '#/components/schemas/Lang'
         'theme':
           'type': 'string'
           'description': 'Interface theme'
@@ -3159,11 +3158,13 @@
       'properties':
         'dns':
           '$ref': '#/components/schemas/CheckConfigRequestInfo'
-        'web':
-          '$ref': '#/components/schemas/CheckConfigRequestInfo'
+        'language':
+          '$ref': '#/components/schemas/Lang'
         'set_static_ip':
           'type': 'boolean'
           'example': false
+        'web':
+          '$ref': '#/components/schemas/CheckConfigRequestInfo'
     'CheckConfigRequestInfo':
       'type': 'object'
       'properties':
@@ -3181,15 +3182,18 @@
       'type': 'object'
       'required':
       - 'dns'
-      - 'web'
+      - 'language'
       - 'static_ip'
+      - 'web'
       'properties':
         'dns':
           '$ref': '#/components/schemas/CheckConfigResponseInfo'
-        'web':
+        'language':
           '$ref': '#/components/schemas/CheckConfigResponseInfo'
         'static_ip':
           '$ref': '#/components/schemas/CheckConfigStaticIpInfo'
+        'web':
+          '$ref': '#/components/schemas/CheckConfigResponseInfo'
     'CheckConfigResponseInfo':
       'type': 'object'
       'required':
@@ -3231,21 +3235,23 @@
       'required':
       - 'dns'
       - 'web'
-      - 'username'
       - 'password'
+      - 'username'
       'properties':
         'dns':
           '$ref': '#/components/schemas/AddressInfo'
         'web':
           '$ref': '#/components/schemas/AddressInfo'
-        'username':
-          'type': 'string'
-          'description': 'Basic auth username'
-          'example': 'admin'
+        'language':
+          '$ref': '#/components/schemas/Lang'
         'password':
-          'type': 'string'
           'description': 'Basic auth password'
           'example': 'password'
+          'type': 'string'
+        'username':
+          'description': 'Basic auth username'
+          'example': 'admin'
+          'type': 'string'
     'Login':
       'type': 'object'
       'description': 'Login request data'
@@ -3267,11 +3273,52 @@
       'description': 'Language settings object.'
       'properties':
         'language':
-          'description': 'The current language or the language to set.'
-          'type': 'string'
+          '$ref': '#/components/schemas/Lang'
       'required':
       - 'language'
       'type': 'object'
+    'Lang':
+      'description': >
+        Language code.
+      # Hold the enum in sync with .twosky.json.
+      'enum':
+      - 'ar'
+      - 'be'
+      - 'bg'
+      - 'cs'
+      - 'da'
+      - 'de'
+      - 'en'
+      - 'es'
+      - 'fa'
+      - 'fi'
+      - 'fr'
+      - 'hr'
+      - 'hu'
+      - 'id'
+      - 'it'
+      - 'ja'
+      - 'ko'
+      - 'nl'
+      - 'no'
+      - 'pl'
+      - 'pt-br'
+      - 'pt-pt'
+      - 'ro'
+      - 'ru'
+      - 'si-lk'
+      - 'sk'
+      - 'sl'
+      - 'sr-cs'
+      - 'sv'
+      - 'th'
+      - 'tr'
+      - 'uk'
+      - 'vi'
+      - 'zh-cn'
+      - 'zh-hk'
+      - 'zh-tw'
+      'type': 'string'
   'securitySchemes':
     'basicAuth':
       'type': 'http'