About Burn Subtitles
Burn Subtitles keeps the complete file workflow inside this browser tab. Your selected file, its name, contents, settings, and generated output are not sent to AntiUpload or a cloud conversion service. Ads and aggregate traffic analytics stay outside the processing boundary and receive no file object or working buffer.
AntiUpload's Burn Subtitles tool turns timed SRT or VTT cues into pixels in the output video. Hard subtitles stay visible because they are part of each frame rather than a separate track; use them when consistent display matters, and keep a soft-caption copy when viewers need to toggle languages or captions off.
The subtitle file is parsed before encoding. The panel reports its timed-cue count, rejects files with no valid timestamps, and previews the first cue with the selected size, exact #RRGGBB colour, outline or translucent box, vertical position, left/centre/right alignment, and edge margin.
Compatible MP4-family sources can use WebCodecs with Canvas rendering; other supported inputs and browsers use FFmpeg WebAssembly with libass. Both paths run locally, preserve audio in the MP4 output, and apply the same selected styling.
How it works
- Drop your video fileAccepts MP4, MOV, WebM, MKV, AVI, M4V, FLV. The video re-encodes during burn (subtitles are pixels-on-frames, not metadata). Output is always MP4.
- Drop your subtitle file (.srt or .vtt)SRT is the most common format (every transcription tool exports it). VTT is the web video standard, used by HTML5 <track> elements. The tool auto-detects from the .srt / .vtt extension.
- Style and preview the first cueChoose one of five sizes, a preset or exact hex colour, outline or translucent box, vertical position, left/centre/right alignment, and compact, standard, or safe margin. The preview updates before export.
- Click Burn subtitlesThe selected browser route re-encodes the video locally and returns an MP4 with captions baked into every applicable frame. Progress confirms the work; duration depends on the source and device.
When to use Burn Subtitles
TikTok / Instagram Reels captions
Social platforms don't reliably show soft subtitles — burning ensures viewers always see them. Pair with auto-generated SRT from our Auto Subtitles tool and pick the TikTok font size for the social-media-feed-competing look.
Captioning a Loom / screen recording for YouTube upload
YouTube has its own auto-caption track, but burning in your own caption file produces higher-quality captions that also display in YouTube's player. Belt-and-suspenders for accessibility compliance.
Hardcoding subtitles for upload to platforms that strip them
Many file-sharing services (Dropbox, Google Drive, embedded players) strip soft subtitle tracks. Burn-in is the workaround that preserves the captions in every distribution channel.
Foreign-language video for an English-speaking audience
Run the source through Auto Subtitles with translate mode → English SRT → burn in. Now the same video shows English captions regardless of player support.
Tutorial videos with software keystrokes / commands captioned
Hand-written caption files documenting specific keystrokes or commands. Burn in for offline reference videos / documentation that ships as MP4.
Putting SRT captions onto an MP4 for a course or LMS
Many learning platforms and video hosts won't show a separate .srt track reliably. Burn the SRT into the MP4 so the captions display the same way for every student, on every device, with no caption settings to fiddle with.
Permanently captioning a video before sending it to someone
When you share an MP4 by email, WhatsApp, or a download link, soft subtitle tracks often get stripped. Burning the captions in means whoever you send it to sees them automatically, no separate file to attach and no instructions needed.
Frequently asked questions
Is it safe and private to burn in subtitles online?
Yes. Your video and subtitle file never leave your device, the burn-in happens entirely in your browser, and once the page has loaded you can even go offline. You can confirm this yourself in the Network tab. Input files are read from browser memory and the output is created locally for your download. AntiUpload does not send file bytes, names, sizes, page counts, contents, passwords, or generated outputs through analytics or advertising requests.
How to add hardcoded subtitles to video for free?
Drop your video and SRT/VTT into AntiUpload Burn Subtitles. Confirm the parsed cue count, style the first-cue preview, then burn. The MP4 output has no watermark, sign-up, or upload step.
What's the difference between soft and hard subtitles?
Soft subtitles (the .srt file as a separate track in the container) are toggleable — viewers can turn them off. Hard subtitles (this tool) are pixels in the video — always visible, can't be removed, work on every player. Pick hard when you need guaranteed visibility (social media, embedded video). Pick soft when viewer choice matters (movies with multiple language tracks).
Why are my captions yellow with a black outline?
Yellow with a black outline is the starting style, not a restriction. Choose a preset or exact hex text colour, an outline or translucent box, five sizes, three vertical positions, three horizontal alignments, and three edge margins while checking the preview.
Best free no-watermark subtitle burner online?
AntiUpload Burn Subtitles — no watermark, no signup, no daily quota, no upload. The libass renderer (Plex / Kodi / mpv use this) handles RTL languages, complex fonts, anti-aliased text, drop shadows, outlines — same fidelity as desktop tools at no cost.
Does this work for ASS / SSA subtitle files?
This tool accepts SRT and VTT. ASS and SSA can contain per-cue fonts, animation, karaoke, and other styling that this plain-cue workflow does not preserve; convert them to SRT or VTT only when that styling loss is acceptable.
Can I use my own font?
The current workflow uses its bundled sans-serif rendering stack so the WebCodecs and FFmpeg outputs stay consistent. You can customize size, exact colour, background, placement, alignment, and margin, but not upload a font file here.
How long does burn-in take?
Burn-in must decode and re-encode the full video. Source duration, resolution, codec, browser, and device all affect runtime, so there is no reliable fixed estimate. Keep the page open and use the progress indicator as the source of truth.
What's the maximum video file size I can caption?
There's no fixed upload limit because nothing is uploaded, so the practical ceiling is your device's memory rather than a server cap. Very long or high-resolution videos use more RAM, so on lower-end machines a shorter clip will be smoother.
.srt vs .vtt — which subtitle file should I use?
Both formats are accepted here, so use whichever your subtitle editor exports. .srt is the most common plain-text format, while .vtt (WebVTT) is the web-native one.
How do I add subtitles to an MP4?
Drop your MP4 into AntiUpload Burn Subtitles, then add your .srt or .vtt subtitle file in the second picker, pick a font size, and click Burn subtitles. The captions are baked into the picture and the output is an MP4 that shows them on any player. It also accepts MOV, WebM, MKV, AVI, M4V and FLV as the source video, but the result is always MP4.
How do I add an SRT file to an MP4?
Add the MP4 as your video and the .srt file in the subtitle picker, then click Burn subtitles. This draws the SRT text into every frame (hard subtitles), so they're always visible and can't be turned off. If instead you want the SRT kept as a separate, toggleable track, that's a different operation called muxing, which this tool doesn't do, it always bakes the captions in.