Drop a video and its .srt — the subtitles are rendered into the picture itself, so they play everywhere, on your own device.
Just drop a video — type your captions right here, no subtitle file needed · everything stays on your device
No size limit · files are processed on your device and never uploaded · how it works
Runs in your browser. Files are never uploaded — you can go offline after the page loads.
How to use the Add Subtitles to Video
Drop a video and its .srt or .vtt file together.
Pick the text size — then burn.
Download the subtitled MP4 and preview it.
Easy to use
Drop files, pick options, download. Whole folders at once, no signup, no daily limit.
Best quality
The same engines the professionals use — SVGO, resvg, MozJPEG, libwebp, libavif — compiled to run in your browser.
Private & secure
Files are processed on your device and never uploaded. Close the tab and nothing remains anywhere.
Why burned-in captions win on social
Most social video plays muted, which means captions are not an accessibility extra — they are the script. Soft
subtitle tracks (a separate file the player can toggle) simply do not exist in most feeds, so the working standard
is hard subs: text rendered permanently into the frames. That is what this tool does, with the same subtitle
engine (libass) professional encoders use, running in your browser.
The style is deliberately clean — bold white with a dark outline, readable on any footage. Timing comes straight
from your SRT/VTT; if you have a VTT and need an SRT (or vice versa), the subtitle
converter swaps formats losslessly. Re-encoding runs at roughly real-time speed, and the video never leaves
your device.
Frequently asked questions
Hard subs vs soft subs — which is this?
Hard subs: the text is rendered into the video frames permanently, so it shows up everywhere — every player, every social platform, no settings. Soft subs (a separate track the viewer can toggle) need player support that social feeds mostly lack, which is why burned-in captions are the standard for social video.
Where do I get an SRT file?
Most transcription services and editing apps export SRT; YouTube lets you download captions as SRT too. The format is also simple enough to write by hand in a text editor — numbered blocks of timing plus text.
How long does burning take?
About the length of the video — the re-encode runs at roughly real-time speed in your browser, and the video never uploads anywhere.
Most online converters upload your file to a server. InfyTool ships the actual encoders to your browser as WebAssembly instead, so processing happens inside your tab — faster for batches, and nothing to delete afterwards.
No upload, ever. Turn off Wi-Fi after the page loads and every tool keeps working.
No limits. No file-size cap, no queue, no watermark, no account.
Runs on your CPU. Batches use several cores in parallel; nothing is throttled.