diff --git a/custom/conf/app.example.ini b/custom/conf/app.example.ini
index b3896bc31..91f86da5f 100644
--- a/custom/conf/app.example.ini
+++ b/custom/conf/app.example.ini
@@ -2338,6 +2338,8 @@ LEVEL = Info
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; Set the maximum number of characters in a mermaid source. (Set to -1 to disable limits)
 ;MERMAID_MAX_SOURCE_CHARACTERS = 5000
+;; Set the maximum number of lines allowed for a filepreview. (Set to -1 to disable limits; set to 0 to disable the feature)
+;FILEPREVIEW_MAX_LINES = 50
 
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
diff --git a/modules/markup/file_preview.go b/modules/markup/file_preview.go
index 3e76dcb8a..32683c317 100644
--- a/modules/markup/file_preview.go
+++ b/modules/markup/file_preview.go
@@ -4,6 +4,7 @@
 package markup
 
 import (
+	"bufio"
 	"bytes"
 	"html/template"
 	"regexp"
@@ -12,6 +13,7 @@ import (
 	"strings"
 
 	"code.gitea.io/gitea/modules/charset"
+	"code.gitea.io/gitea/modules/highlight"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/setting"
 	"code.gitea.io/gitea/modules/translation"
@@ -31,9 +33,15 @@ type FilePreview struct {
 	filePath    string
 	start       int
 	end         int
+	isTruncated bool
 }
 
 func NewFilePreview(ctx *RenderContext, node *html.Node, locale translation.Locale) *FilePreview {
+	if (setting.FilePreviewMaxLines == 0) {
+		// Feature is disabled
+		return nil
+	}
+
 	preview := &FilePreview{}
 
 	m := filePreviewPattern.FindStringSubmatchIndex(node.Data)
@@ -63,18 +71,20 @@ func NewFilePreview(ctx *RenderContext, node *html.Node, locale translation.Loca
 	preview.end = m[1]
 
 	projPathSegments := strings.Split(projPath, "/")
-	fileContent, err := DefaultProcessorHelper.GetRepoFileContent(
+	var language string
+	fileBlob, err := DefaultProcessorHelper.GetRepoFileBlob(
 		ctx.Ctx,
 		projPathSegments[len(projPathSegments)-2],
 		projPathSegments[len(projPathSegments)-1],
 		commitSha, preview.filePath,
+		&language,
 	)
 	if err != nil {
 		return nil
 	}
 
 	lineSpecs := strings.Split(hash, "-")
-	lineCount := len(fileContent)
+	// lineCount := len(fileContent)
 
 	commitLinkBuffer := new(bytes.Buffer)
 	err = html.Render(commitLinkBuffer, createLink(node.Data[m[0]:m[5]], commitSha[0:7], "text black"))
@@ -82,28 +92,31 @@ func NewFilePreview(ctx *RenderContext, node *html.Node, locale translation.Loca
 		log.Error("failed to render commitLink: %v", err)
 	}
 
-	if len(lineSpecs) == 1 {
-		line, _ := strconv.Atoi(strings.TrimPrefix(lineSpecs[0], "L"))
-		if line < 1 || line > lineCount {
-			return nil
-		}
+	var startLine, endLine int
 
-		preview.fileContent = fileContent[line-1 : line]
+	if len(lineSpecs) == 1 {
+		startLine, _ = strconv.Atoi(strings.TrimPrefix(lineSpecs[0], "L"))
+		endLine = startLine
+		// if line < 1 || line > lineCount {
+		// 	return nil
+		// }
+
+		// preview.fileContent = fileContent[line-1 : line]
 		preview.subTitle = locale.Tr(
-			"markup.filepreview.line", line,
+			"markup.filepreview.line", startLine,
 			template.HTML(commitLinkBuffer.String()),
 		)
 
-		preview.lineOffset = line - 1
+		preview.lineOffset = startLine - 1
 	} else {
-		startLine, _ := strconv.Atoi(strings.TrimPrefix(lineSpecs[0], "L"))
-		endLine, _ := strconv.Atoi(strings.TrimPrefix(lineSpecs[1], "L"))
+		startLine, _ = strconv.Atoi(strings.TrimPrefix(lineSpecs[0], "L"))
+		endLine, _ = strconv.Atoi(strings.TrimPrefix(lineSpecs[1], "L"))
 
-		if startLine < 1 || endLine < 1 || startLine > lineCount || endLine > lineCount || endLine < startLine {
-			return nil
-		}
+		// if startLine < 1 || endLine < 1 || startLine > lineCount || endLine > lineCount || endLine < startLine {
+		// 	return nil
+		// }
 
-		preview.fileContent = fileContent[startLine-1 : endLine]
+		// preview.fileContent = fileContent[startLine-1 : endLine]
 		preview.subTitle = locale.Tr(
 			"markup.filepreview.lines", startLine, endLine,
 			template.HTML(commitLinkBuffer.String()),
@@ -112,6 +125,50 @@ func NewFilePreview(ctx *RenderContext, node *html.Node, locale translation.Loca
 		preview.lineOffset = startLine - 1
 	}
 
+	lineCount := endLine - (startLine-1)
+	if startLine < 1 || endLine < 1 || lineCount < 1 {
+		return nil
+	}
+
+	if setting.FilePreviewMaxLines > 0 && lineCount > setting.FilePreviewMaxLines {
+		preview.isTruncated = true
+		lineCount = setting.FilePreviewMaxLines
+	}
+
+	dataRc, err := fileBlob.DataAsync()
+	if err != nil {
+		return nil
+	}
+	defer dataRc.Close()
+
+	reader := bufio.NewReader(dataRc)
+
+	// skip all lines until we find our startLine
+	for i := 1; i < startLine; i++ {
+		_, err := reader.ReadBytes('\n')
+		if err != nil {
+			return nil
+		}
+	}
+
+	// capture the lines we're interested in
+	lineBuffer := new(bytes.Buffer)
+	for i := 0; i < lineCount; i++ {
+		buf, err := reader.ReadBytes('\n')
+		if err != nil {
+			break;
+		}
+		lineBuffer.Write(buf)
+	}
+
+	// highlight the file...
+	fileContent, _, err := highlight.File(fileBlob.Name(), language, lineBuffer.Bytes())
+	if err != nil {
+		log.Error("highlight.File failed, fallback to plain text: %v", err)
+		fileContent = highlight.PlainText(lineBuffer.Bytes())
+	}
+	preview.fileContent = fileContent
+
 	return preview
 }
 
@@ -258,6 +315,20 @@ func (p *FilePreview) CreateHTML(locale translation.Locale) *html.Node {
 		Attr: []html.Attribute{{Key: "class", Val: "file-preview-box"}},
 	}
 	node.AppendChild(header)
+
+	if (p.isTruncated) {
+		warning := &html.Node{
+			Type: html.ElementNode,
+			Data: atom.Div.String(),
+			Attr: []html.Attribute{{Key: "class", Val: "ui warning message tw-text-left"}},
+		}
+		warning.AppendChild(&html.Node{
+			Type: html.TextNode,
+			Data: locale.TrString("markup.filepreview.truncated"),
+		})
+		node.AppendChild(warning)
+	}
+
 	node.AppendChild(twrapper)
 
 	return node
diff --git a/modules/markup/html.go b/modules/markup/html.go
index 9a04e02fb..4c74a81ba 100644
--- a/modules/markup/html.go
+++ b/modules/markup/html.go
@@ -1059,7 +1059,7 @@ func filePreviewPatternProcessor(ctx *RenderContext, node *html.Node) {
 	if ctx.Metas == nil {
 		return
 	}
-	if DefaultProcessorHelper.GetRepoFileContent == nil {
+	if DefaultProcessorHelper.GetRepoFileBlob == nil {
 		return
 	}
 
diff --git a/modules/markup/renderer.go b/modules/markup/renderer.go
index b6d742e5c..b08c9eb23 100644
--- a/modules/markup/renderer.go
+++ b/modules/markup/renderer.go
@@ -8,7 +8,7 @@ import (
 	"context"
 	"errors"
 	"fmt"
-	"html/template"
+	// "html/template"
 	"io"
 	"net/url"
 	"path/filepath"
@@ -32,7 +32,7 @@ const (
 
 type ProcessorHelper struct {
 	IsUsernameMentionable func(ctx context.Context, username string) bool
-	GetRepoFileContent    func(ctx context.Context, ownerName, repoName, commitSha, filePath string) ([]template.HTML, error)
+	GetRepoFileBlob    func(ctx context.Context, ownerName, repoName, commitSha, filePath string, language *string) (*git.Blob, error)
 
 	ElementDir string // the direction of the elements, eg: "ltr", "rtl", "auto", default to no direction attribute
 }
diff --git a/modules/markup/sanitizer.go b/modules/markup/sanitizer.go
index c37027b84..1048f0e37 100644
--- a/modules/markup/sanitizer.go
+++ b/modules/markup/sanitizer.go
@@ -135,6 +135,7 @@ func createDefaultPolicy() *bluemonday.Policy {
 	policy.AllowAttrs("class").Matching(regexp.MustCompile("^ambiguous-code-point$")).OnElements("span")
 	policy.AllowAttrs("data-tooltip-content").OnElements("span")
 	policy.AllowAttrs("class").Matching(regexp.MustCompile("muted|(text black)")).OnElements("a")
+	policy.AllowAttrs("class").Matching(regexp.MustCompile("^ui warning message tw-text-left$")).OnElements("div")
 
 	// Allow generally safe attributes
 	generalSafeAttrs := []string{
diff --git a/modules/setting/markup.go b/modules/setting/markup.go
index 6c2246342..e893c1c2f 100644
--- a/modules/setting/markup.go
+++ b/modules/setting/markup.go
@@ -15,6 +15,7 @@ var (
 	ExternalMarkupRenderers    []*MarkupRenderer
 	ExternalSanitizerRules     []MarkupSanitizerRule
 	MermaidMaxSourceCharacters int
+	FilePreviewMaxLines        int
 )
 
 const (
@@ -62,6 +63,7 @@ func loadMarkupFrom(rootCfg ConfigProvider) {
 	mustMapSetting(rootCfg, "markdown", &Markdown)
 
 	MermaidMaxSourceCharacters = rootCfg.Section("markup").Key("MERMAID_MAX_SOURCE_CHARACTERS").MustInt(5000)
+	FilePreviewMaxLines = rootCfg.Section("markup").Key("FILEPREVIEW_MAX_LINES").MustInt(50)
 	ExternalMarkupRenderers = make([]*MarkupRenderer, 0, 10)
 	ExternalSanitizerRules = make([]MarkupSanitizerRule, 0, 10)
 
diff --git a/options/locale/locale_en-US.ini b/options/locale/locale_en-US.ini
index efaf8b72c..8533cf065 100644
--- a/options/locale/locale_en-US.ini
+++ b/options/locale/locale_en-US.ini
@@ -3711,3 +3711,4 @@ submodule = Submodule
 [markup]
 filepreview.line = Line %[1]d in %[2]s
 filepreview.lines = Lines %[1]d to %[2]d in %[3]s
+filepreview.truncated = Preview has been truncated
diff --git a/services/markup/processorhelper.go b/services/markup/processorhelper.go
index df96f25ce..98a7824a6 100644
--- a/services/markup/processorhelper.go
+++ b/services/markup/processorhelper.go
@@ -6,15 +6,17 @@ package markup
 import (
 	"context"
 	"fmt"
-	"html/template"
-	"io"
+
+	// "html/template"
+	// "io"
 
 	"code.gitea.io/gitea/models/perm/access"
 	"code.gitea.io/gitea/models/repo"
 	"code.gitea.io/gitea/models/unit"
 	"code.gitea.io/gitea/models/user"
+	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/gitrepo"
-	"code.gitea.io/gitea/modules/highlight"
+	// "code.gitea.io/gitea/modules/highlight"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/markup"
 	gitea_context "code.gitea.io/gitea/services/context"
@@ -39,7 +41,7 @@ func ProcessorHelper() *markup.ProcessorHelper {
 			// when using gitea context (web context), use user's visibility and user's permission to check
 			return user.IsUserVisibleToViewer(giteaCtx, mentionedUser, giteaCtx.Doer)
 		},
-		GetRepoFileContent: func(ctx context.Context, ownerName, repoName, commitSha, filePath string) ([]template.HTML, error) {
+		GetRepoFileBlob: func(ctx context.Context, ownerName, repoName, commitSha, filePath string, language *string) (*git.Blob, error) {
 			repo, err := repo.GetRepositoryByOwnerAndName(ctx, ownerName, repoName)
 			if err != nil {
 				return nil, err
@@ -70,9 +72,11 @@ func ProcessorHelper() *markup.ProcessorHelper {
 				return nil, err
 			}
 
-			language, err := file_service.TryGetContentLanguage(gitRepo, commitSha, filePath)
-			if err != nil {
-				log.Error("Unable to get file language for %-v:%s. Error: %v", repo, filePath, err)
+			if language != nil {
+				*language, err = file_service.TryGetContentLanguage(gitRepo, commitSha, filePath)
+				if err != nil {
+					log.Error("Unable to get file language for %-v:%s. Error: %v", repo, filePath, err)
+				}
 			}
 
 			blob, err := commit.GetBlobByPath(filePath)
@@ -80,7 +84,9 @@ func ProcessorHelper() *markup.ProcessorHelper {
 				return nil, err
 			}
 
-			dataRc, err := blob.DataAsync()
+			return blob, nil
+
+			/*dataRc, err := blob.DataAsync()
 			if err != nil {
 				return nil, err
 			}
@@ -97,7 +103,7 @@ func ProcessorHelper() *markup.ProcessorHelper {
 				fileContent = highlight.PlainText(buf)
 			}
 
-			return fileContent, nil
+			return fileContent, nil*/
 		},
 	}
 }
diff --git a/web_src/css/markup/filepreview.css b/web_src/css/markup/filepreview.css
index 69360e2a7..d2ec16ea8 100644
--- a/web_src/css/markup/filepreview.css
+++ b/web_src/css/markup/filepreview.css
@@ -25,6 +25,12 @@
   background: var(--color-box-header);
 }
 
+.markup .file-preview-box .warning {
+  border-radius: 0;
+  margin: 0;
+  padding: .5rem .5rem .5rem 1rem;
+}
+
 .markup .file-preview-box .header > a {
   display: block;
 }