diff --git a/models/repo/avatar.go b/models/repo/avatar.go
index 72ee938ada..a891a9c735 100644
--- a/models/repo/avatar.go
+++ b/models/repo/avatar.go
@@ -9,10 +9,10 @@ import (
 	"image/png"
 	"io"
 	"net/url"
-	"strings"
 
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/avatar"
+	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/storage"
@@ -86,11 +86,5 @@ func (repo *Repository) relAvatarLink(ctx context.Context) string {
 
 // AvatarLink returns a link to the repository's avatar.
 func (repo *Repository) AvatarLink(ctx context.Context) string {
-	link := repo.relAvatarLink(ctx)
-	// we only prepend our AppURL to our known (relative, internal) avatar link to get an absolute URL
-	if strings.HasPrefix(link, "/") && !strings.HasPrefix(link, "//") {
-		return setting.AppURL + strings.TrimPrefix(link, setting.AppSubURL)[1:]
-	}
-	// otherwise, return the link as it is
-	return link
+	return httplib.MakeAbsoluteURL(ctx, repo.relAvatarLink(ctx))
 }
diff --git a/models/user/avatar.go b/models/user/avatar.go
index c6937d7b51..b38d3c35b6 100644
--- a/models/user/avatar.go
+++ b/models/user/avatar.go
@@ -9,11 +9,11 @@ import (
 	"fmt"
 	"image/png"
 	"io"
-	"strings"
 
 	"code.gitea.io/gitea/models/avatars"
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/avatar"
+	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/storage"
@@ -91,11 +91,7 @@ func (u *User) AvatarLinkWithSize(ctx context.Context, size int) string {
 
 // AvatarLink returns the full avatar link with http host
 func (u *User) AvatarLink(ctx context.Context) string {
-	link := u.AvatarLinkWithSize(ctx, 0)
-	if !strings.HasPrefix(link, "//") && !strings.Contains(link, "://") {
-		return setting.AppURL + strings.TrimPrefix(link, setting.AppSubURL+"/")
-	}
-	return link
+	return httplib.MakeAbsoluteURL(ctx, u.AvatarLinkWithSize(ctx, 0))
 }
 
 // IsUploadAvatarChanged returns true if the current user's avatar would be changed with the provided data
diff --git a/modules/httplib/url.go b/modules/httplib/url.go
index 903799cb68..05d3f0f51a 100644
--- a/modules/httplib/url.go
+++ b/modules/httplib/url.go
@@ -4,6 +4,8 @@
 package httplib
 
 import (
+	"context"
+	"net/http"
 	"net/url"
 	"strings"
 
@@ -11,6 +13,10 @@ import (
 	"code.gitea.io/gitea/modules/util"
 )
 
+type httpRequestContextKeyStruct struct{}
+
+var HttpRequestContextKey = httpRequestContextKeyStruct{}
+
 func urlIsRelative(s string, u *url.URL) bool {
 	// Unfortunately browsers consider a redirect Location with preceding "//", "\\", "/\" and "\/" as meaning redirect to "http(s)://REST_OF_PATH"
 	// Therefore we should ignore these redirect locations to prevent open redirects
@@ -26,7 +32,60 @@ func IsRelativeURL(s string) bool {
 	return err == nil && urlIsRelative(s, u)
 }
 
-func IsCurrentGiteaSiteURL(s string) bool {
+func guessHttpRequestScheme(req *http.Request) string {
+	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Proto
+	if s := req.Header.Get("X-Forwarded-Proto"); s != "" {
+		return s
+	}
+	if s := req.Header.Get("X-Forwarded-Protocol"); s != "" {
+		return s
+	}
+	if s := req.Header.Get("X-Url-Scheme"); s != "" {
+		return s
+	}
+	if s := req.Header.Get("Front-End-Https"); s != "" {
+		return util.Iif(s == "on", "https", "http")
+	}
+	if s := req.Header.Get("X-Forwarded-Ssl"); s != "" {
+		return util.Iif(s == "on", "https", "http")
+	}
+	if req.TLS != nil {
+		return "https"
+	}
+	return "http"
+}
+
+func guessHttpRequestHost(req *http.Request) string {
+	// https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Forwarded-Host
+	if s := req.Header.Get("X-Forwarded-Host"); s != "" {
+		return s
+	}
+	if req.Host != "" {
+		return req.Host // Golang: the Host header is promoted to the Request.Host field and removed from the Header map.
+	}
+	return ""
+}
+
+// GuessCurrentAppURL tries to guess the current full URL by http headers. It always has a '/' suffix, exactly the same as setting.AppURL
+func GuessCurrentAppURL(ctx context.Context) string {
+	req, ok := ctx.Value(HttpRequestContextKey).(*http.Request)
+	if !ok {
+		return setting.AppURL
+	}
+	if host := guessHttpRequestHost(req); host != "" {
+		return guessHttpRequestScheme(req) + "://" + host + setting.AppSubURL + "/"
+	}
+	return setting.AppURL
+}
+
+func MakeAbsoluteURL(ctx context.Context, s string) string {
+	if IsRelativeURL(s) {
+		return GuessCurrentAppURL(ctx) + strings.TrimPrefix(s, "/")
+	}
+	return s
+}
+
+func IsCurrentGiteaSiteURL(ctx context.Context, s string) bool {
 	u, err := url.Parse(s)
 	if err != nil {
 		return false
@@ -45,5 +104,6 @@ func IsCurrentGiteaSiteURL(s string) bool {
 	if u.Path == "" {
 		u.Path = "/"
 	}
-	return strings.HasPrefix(strings.ToLower(u.String()), strings.ToLower(setting.AppURL))
+	urlLower := strings.ToLower(u.String())
+	return strings.HasPrefix(urlLower, strings.ToLower(setting.AppURL)) || strings.HasPrefix(urlLower, strings.ToLower(GuessCurrentAppURL(ctx)))
 }
diff --git a/modules/httplib/url_test.go b/modules/httplib/url_test.go
index 9bf09bcf2f..05c151baa0 100644
--- a/modules/httplib/url_test.go
+++ b/modules/httplib/url_test.go
@@ -4,6 +4,7 @@
 package httplib
 
 import (
+	"context"
 	"testing"
 
 	"code.gitea.io/gitea/modules/setting"
@@ -40,6 +41,7 @@ func TestIsRelativeURL(t *testing.T) {
 func TestIsCurrentGiteaSiteURL(t *testing.T) {
 	defer test.MockVariableValue(&setting.AppURL, "http://localhost:3000/sub/")()
 	defer test.MockVariableValue(&setting.AppSubURL, "/sub")()
+	ctx := context.Background()
 	good := []string{
 		"?key=val",
 		"/sub",
@@ -50,7 +52,7 @@ func TestIsCurrentGiteaSiteURL(t *testing.T) {
 		"http://localhost:3000/sub/",
 	}
 	for _, s := range good {
-		assert.True(t, IsCurrentGiteaSiteURL(s), "good = %q", s)
+		assert.True(t, IsCurrentGiteaSiteURL(ctx, s), "good = %q", s)
 	}
 	bad := []string{
 		".",
@@ -64,13 +66,13 @@ func TestIsCurrentGiteaSiteURL(t *testing.T) {
 		"http://other/",
 	}
 	for _, s := range bad {
-		assert.False(t, IsCurrentGiteaSiteURL(s), "bad = %q", s)
+		assert.False(t, IsCurrentGiteaSiteURL(ctx, s), "bad = %q", s)
 	}
 
 	setting.AppURL = "http://localhost:3000/"
 	setting.AppSubURL = ""
-	assert.False(t, IsCurrentGiteaSiteURL("//"))
-	assert.False(t, IsCurrentGiteaSiteURL("\\\\"))
-	assert.False(t, IsCurrentGiteaSiteURL("http://localhost"))
-	assert.True(t, IsCurrentGiteaSiteURL("http://localhost:3000?key=val"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "//"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "\\\\"))
+	assert.False(t, IsCurrentGiteaSiteURL(ctx, "http://localhost"))
+	assert.True(t, IsCurrentGiteaSiteURL(ctx, "http://localhost:3000?key=val"))
 }
diff --git a/modules/markup/html_codepreview.go b/modules/markup/html_codepreview.go
index 5ef2217e3d..5ab9290b3e 100644
--- a/modules/markup/html_codepreview.go
+++ b/modules/markup/html_codepreview.go
@@ -42,7 +42,7 @@ func renderCodeBlock(ctx *RenderContext, node *html.Node) (urlPosStart, urlPosSt
 		CommitID:  node.Data[m[6]:m[7]],
 		FilePath:  node.Data[m[8]:m[9]],
 	}
-	if !httplib.IsCurrentGiteaSiteURL(opts.FullURL) {
+	if !httplib.IsCurrentGiteaSiteURL(ctx.Ctx, opts.FullURL) {
 		return 0, 0, "", nil
 	}
 	u, err := url.Parse(opts.FilePath)
diff --git a/routers/api/actions/artifacts.go b/routers/api/actions/artifacts.go
index 5bd004bd37..35e3ee6906 100644
--- a/routers/api/actions/artifacts.go
+++ b/routers/api/actions/artifacts.go
@@ -71,6 +71,7 @@ import (
 
 	"code.gitea.io/gitea/models/actions"
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
@@ -184,8 +185,8 @@ type artifactRoutes struct {
 	fs     storage.ObjectStorage
 }
 
-func (ar artifactRoutes) buildArtifactURL(runID int64, artifactHash, suffix string) string {
-	uploadURL := strings.TrimSuffix(setting.AppURL, "/") + strings.TrimSuffix(ar.prefix, "/") +
+func (ar artifactRoutes) buildArtifactURL(ctx *ArtifactContext, runID int64, artifactHash, suffix string) string {
+	uploadURL := strings.TrimSuffix(httplib.GuessCurrentAppURL(ctx), "/") + strings.TrimSuffix(ar.prefix, "/") +
 		strings.ReplaceAll(artifactRouteBase, "{run_id}", strconv.FormatInt(runID, 10)) +
 		"/" + artifactHash + "/" + suffix
 	return uploadURL
@@ -224,7 +225,7 @@ func (ar artifactRoutes) getUploadArtifactURL(ctx *ArtifactContext) {
 	// use md5(artifact_name) to create upload url
 	artifactHash := fmt.Sprintf("%x", md5.Sum([]byte(req.Name)))
 	resp := getUploadArtifactResponse{
-		FileContainerResourceURL: ar.buildArtifactURL(runID, artifactHash, "upload"+retentionQuery),
+		FileContainerResourceURL: ar.buildArtifactURL(ctx, runID, artifactHash, "upload"+retentionQuery),
 	}
 	log.Debug("[artifact] get upload url: %s", resp.FileContainerResourceURL)
 	ctx.JSON(http.StatusOK, resp)
@@ -365,7 +366,7 @@ func (ar artifactRoutes) listArtifacts(ctx *ArtifactContext) {
 		artifactHash := fmt.Sprintf("%x", md5.Sum([]byte(art.ArtifactName)))
 		item := listArtifactsResponseItem{
 			Name:                     art.ArtifactName,
-			FileContainerResourceURL: ar.buildArtifactURL(runID, artifactHash, "download_url"),
+			FileContainerResourceURL: ar.buildArtifactURL(ctx, runID, artifactHash, "download_url"),
 		}
 		items = append(items, item)
 		values[art.ArtifactName] = true
@@ -437,7 +438,7 @@ func (ar artifactRoutes) getDownloadArtifactURL(ctx *ArtifactContext) {
 			}
 		}
 		if downloadURL == "" {
-			downloadURL = ar.buildArtifactURL(runID, strconv.FormatInt(artifact.ID, 10), "download")
+			downloadURL = ar.buildArtifactURL(ctx, runID, strconv.FormatInt(artifact.ID, 10), "download")
 		}
 		item := downloadArtifactResponseItem{
 			Path:            util.PathJoinRel(itemPath, artifact.ArtifactPath),
diff --git a/routers/api/actions/artifactsv4.go b/routers/api/actions/artifactsv4.go
index 8300989c75..dde9caf4f2 100644
--- a/routers/api/actions/artifactsv4.go
+++ b/routers/api/actions/artifactsv4.go
@@ -92,6 +92,7 @@ import (
 
 	"code.gitea.io/gitea/models/actions"
 	"code.gitea.io/gitea/models/db"
+	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/storage"
@@ -160,9 +161,9 @@ func (r artifactV4Routes) buildSignature(endp, expires, artifactName string, tas
 	return mac.Sum(nil)
 }
 
-func (r artifactV4Routes) buildArtifactURL(endp, artifactName string, taskID int64) string {
+func (r artifactV4Routes) buildArtifactURL(ctx *ArtifactContext, endp, artifactName string, taskID int64) string {
 	expires := time.Now().Add(60 * time.Minute).Format("2006-01-02 15:04:05.999999999 -0700 MST")
-	uploadURL := strings.TrimSuffix(setting.AppURL, "/") + strings.TrimSuffix(r.prefix, "/") +
+	uploadURL := strings.TrimSuffix(httplib.GuessCurrentAppURL(ctx), "/") + strings.TrimSuffix(r.prefix, "/") +
 		"/" + endp + "?sig=" + base64.URLEncoding.EncodeToString(r.buildSignature(endp, expires, artifactName, taskID)) + "&expires=" + url.QueryEscape(expires) + "&artifactName=" + url.QueryEscape(artifactName) + "&taskID=" + fmt.Sprint(taskID)
 	return uploadURL
 }
@@ -278,7 +279,7 @@ func (r *artifactV4Routes) createArtifact(ctx *ArtifactContext) {
 
 	respData := CreateArtifactResponse{
 		Ok:              true,
-		SignedUploadUrl: r.buildArtifactURL("UploadArtifact", artifactName, ctx.ActionTask.ID),
+		SignedUploadUrl: r.buildArtifactURL(ctx, "UploadArtifact", artifactName, ctx.ActionTask.ID),
 	}
 	r.sendProtbufBody(ctx, &respData)
 }
@@ -454,7 +455,7 @@ func (r *artifactV4Routes) getSignedArtifactURL(ctx *ArtifactContext) {
 		}
 	}
 	if respData.SignedUrl == "" {
-		respData.SignedUrl = r.buildArtifactURL("DownloadArtifact", artifactName, ctx.ActionTask.ID)
+		respData.SignedUrl = r.buildArtifactURL(ctx, "DownloadArtifact", artifactName, ctx.ActionTask.ID)
 	}
 	r.sendProtbufBody(ctx, &respData)
 }
diff --git a/routers/api/packages/container/container.go b/routers/api/packages/container/container.go
index 2cb16daebc..1efd166eb3 100644
--- a/routers/api/packages/container/container.go
+++ b/routers/api/packages/container/container.go
@@ -17,6 +17,7 @@ import (
 	packages_model "code.gitea.io/gitea/models/packages"
 	container_model "code.gitea.io/gitea/models/packages/container"
 	user_model "code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/json"
 	"code.gitea.io/gitea/modules/log"
 	packages_module "code.gitea.io/gitea/modules/packages"
@@ -115,7 +116,7 @@ func apiErrorDefined(ctx *context.Context, err *namedError) {
 }
 
 func apiUnauthorizedError(ctx *context.Context) {
-	ctx.Resp.Header().Add("WWW-Authenticate", `Bearer realm="`+setting.AppURL+`v2/token",service="container_registry",scope="*"`)
+	ctx.Resp.Header().Add("WWW-Authenticate", `Bearer realm="`+httplib.GuessCurrentAppURL(ctx)+`v2/token",service="container_registry",scope="*"`)
 	apiErrorDefined(ctx, errUnauthorized)
 }
 
diff --git a/routers/common/middleware.go b/routers/common/middleware.go
index c7c75fb099..ec54659298 100644
--- a/routers/common/middleware.go
+++ b/routers/common/middleware.go
@@ -4,11 +4,13 @@
 package common
 
 import (
+	go_context "context"
 	"fmt"
 	"net/http"
 	"strings"
 
 	"code.gitea.io/gitea/modules/cache"
+	"code.gitea.io/gitea/modules/httplib"
 	"code.gitea.io/gitea/modules/process"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/web/middleware"
@@ -34,6 +36,7 @@ func ProtocolMiddlewares() (handlers []any) {
 				}
 			}()
 			req = req.WithContext(middleware.WithContextData(req.Context()))
+			req = req.WithContext(go_context.WithValue(req.Context(), httplib.HttpRequestContextKey, req))
 			next.ServeHTTP(resp, req)
 		})
 	})
diff --git a/routers/common/redirect.go b/routers/common/redirect.go
index 34044e814b..d64f74ec82 100644
--- a/routers/common/redirect.go
+++ b/routers/common/redirect.go
@@ -17,7 +17,7 @@ func FetchRedirectDelegate(resp http.ResponseWriter, req *http.Request) {
 	// The typical page is "issue comment" page. The backend responds "/owner/repo/issues/1#comment-2",
 	// then frontend needs this delegate to redirect to the new location with hash correctly.
 	redirect := req.PostFormValue("redirect")
-	if !httplib.IsCurrentGiteaSiteURL(redirect) {
+	if !httplib.IsCurrentGiteaSiteURL(req.Context(), redirect) {
 		resp.WriteHeader(http.StatusBadRequest)
 		return
 	}
diff --git a/routers/web/auth/auth.go b/routers/web/auth/auth.go
index 7c873796fe..4083d64226 100644
--- a/routers/web/auth/auth.go
+++ b/routers/web/auth/auth.go
@@ -368,7 +368,7 @@ func handleSignInFull(ctx *context.Context, u *user_model.User, remember, obeyRe
 		return setting.AppSubURL + "/"
 	}
 
-	if redirectTo := ctx.GetSiteCookie("redirect_to"); redirectTo != "" && httplib.IsCurrentGiteaSiteURL(redirectTo) {
+	if redirectTo := ctx.GetSiteCookie("redirect_to"); redirectTo != "" && httplib.IsCurrentGiteaSiteURL(ctx, redirectTo) {
 		middleware.DeleteRedirectToCookie(ctx.Resp)
 		if obeyRedirect {
 			ctx.RedirectToCurrentSite(redirectTo)
diff --git a/services/context/base.go b/services/context/base.go
index 05b8ab1b9b..29e62ae389 100644
--- a/services/context/base.go
+++ b/services/context/base.go
@@ -254,7 +254,7 @@ func (b *Base) Redirect(location string, status ...int) {
 		code = status[0]
 	}
 
-	if strings.HasPrefix(location, "http://") || strings.HasPrefix(location, "https://") || strings.HasPrefix(location, "//") {
+	if !httplib.IsRelativeURL(location) {
 		// Some browsers (Safari) have buggy behavior for Cookie + Cache + External Redirection, eg: /my-path => https://other/path
 		// 1. the first request to "/my-path" contains cookie
 		// 2. some time later, the request to "/my-path" doesn't contain cookie (caused by Prevent web tracking)
diff --git a/services/context/context_response.go b/services/context/context_response.go
index 87c34c35ed..c43a649b49 100644
--- a/services/context/context_response.go
+++ b/services/context/context_response.go
@@ -52,7 +52,7 @@ func (ctx *Context) RedirectToCurrentSite(location ...string) {
 			continue
 		}
 
-		if !httplib.IsCurrentGiteaSiteURL(loc) {
+		if !httplib.IsCurrentGiteaSiteURL(ctx, loc) {
 			continue
 		}