Use the free Add Subtitles to Video tool below: burn SRT captions into your MP4 or WebM video, right in your browser. Your files never leave your device.
What Add Subtitles to Video does
Add Subtitles to Video burns subtitles straight into the picture of your video. You give it a video file and an SRT subtitle file, and it produces a new video where the words appear on screen at the times written in the SRT file. The captions become part of the video itself, so they show up on any player, even players that do not support separate subtitle tracks.
Everything happens in your browser. Your video and your SRT file are never uploaded to a server, and you never need an account. The tool works with MP4, WebM, and MOV files, as long as your browser can play them. If a video will not play in your browser, this tool cannot use it either.
How to use the subtitles tool
First, check the format line at the top of the tool. It tells you the exact output format your browser will produce, before you start. In Chrome and Edge that is usually MP4. In Firefox it is WebM. Next, choose your video file, then choose your SRT file, or paste the SRT text into the box. The tool reads the SRT file and tells you how many cues it found and shows the first cue.
Then pick a subtitle size and a position: bottom or top of the frame. Press the captioned preview button to watch the video with the captions drawn on the frame, so you can check the timing and the size. When it looks right, press the burn button. The tool plays the video from the start and records it with the captions drawn on every frame, so processing takes about the length of the video. When it finishes, watch the subtitled video in the preview player and download it.
Worked example: two cues burned into a 4-second video
Here is a real test we ran with this tool. We started with a video that was 4.0 seconds long, 320 by 240 pixels, and 59.0 KB in size, with a sound track. The SRT file had two cues. The first cue said Hello world, from 0.5 seconds to 1.5 seconds. The second cue had two lines, Second cue here and line two, from 2.0 seconds to 3.25 seconds.
The tool produced a subtitled video of 4.24 seconds and 239,782 bytes, saved as MP4. The sound track was kept, the frame stayed 320 by 240 pixels, and both cues appeared on screen at their SRT times. We checked the caption directly: a frame from the output at 1.0 second differed strongly from the original in the bottom caption band, while the top barely changed. That is what a real burned-in caption looks like.
What stays the same, and what changes
The length, the frame size, and the sound of your video stay the same. The only thing added is the caption text on the picture, at the times your SRT file sets. What changes is the file itself: the subtitled video is re-encoded from scratch. That means the file size can grow or shrink compared with the original, and the picture quality can drop slightly, especially if the original was already heavily compressed.
The captions are permanent: once burned in, they cannot be switched off. Keep your original video and SRT file, in case you want a different size or a corrected caption later.
Honest limitations
The styling is basic only. You get white text on a dark bar, in three sizes, at the bottom or the top of the frame. You cannot pick fonts, colors, or fancy outlines, and you cannot move a single cue to a different spot. The SRT timing drives the text completely: if a cue starts late in your SRT file, it appears late in the video, and the tool will not fix bad timing for you.
The output is re-encoded, never lossless, and processing takes about the length of the video, with the browser tab open while it works. Very long videos take a long time. Overlapping cues are shown one at a time, starting with the earliest.
Good uses for burned-in subtitles
This tool fits everyday jobs. Add captions to a short clip before posting it somewhere that plays videos silently. Make a tutorial clip readable for viewers who watch with the sound off. Caption a family video for a relative who is hard of hearing. Prepare a clip for a classroom screen where the sound cannot be turned up. For short videos where the words must be visible everywhere, burning them in is the simplest reliable option.
Frequently asked questions
Do I need a separate SRT file? Yes. This tool does not create subtitles from speech. You bring the SRT file, and the tool burns its text into the video at its times.
Will the captions show on every player? Yes. Because the words are drawn into the picture itself, any player that plays the video shows them. There is no subtitle track to turn on.
Can I change the caption style? Only size and position: small, medium, or large, at the bottom or the top. The style is white text on a dark bar, and that is a deliberate limit of this free browser tool.
Do my video and subtitles leave my device? No. The whole job runs in your browser. Nothing is uploaded, and no account is needed.
Spanish version: Anadir Subtitulos a Video Online