Add Subtitles to Video Online Free

Why this route costs nothing

A subtitled video needs three things: timed text, a look for that text, and a new copy of the video with the text drawn on every frame. When you provide the text yourself, all three happen inside your browser tab. Your computer decodes the video, draws the lines and encodes the result, so there is no server time to bill and nothing to meter.

The single step that runs on mydubly's servers is AI transcription, and it is the only thing credits are for. Leave it out and the whole job, from opening the file to saving the MP4, is free.

First, switch the AI off

The option "Write the subtitles automatically with AI" is ticked when you first open the editor, and your browser remembers whatever you chose last time. If it is on when you pick a video, the editor tries to start an AI run: signed out, a Google sign-in window opens; signed in, the run starts and uses credits.

So untick it before choosing the file. If you've already picked a video with it ticked and the sign-in window appeared, close the window and then either import your SRT or VTT, which cancels the waiting run, or reload the page, untick the switch and choose the video again. Simply closing the window isn't enough on its own, because signing in later in that session would start the run.

The free route, step by step

1. Untick "Write the subtitles automatically with AI".
2. Choose your video or drop it on the box. MP4, MOV, M4V, WebM and MKV files open.
3. Bring in the words. Click Import SRT / VTT for a file you already have, or play the video and press Enter wherever a new line should begin, then type it.
4. Line them up. Drag a line's edges on the timeline, type exact times in the list, or use "Shift all by" when every line is early or late by the same amount.
5. Open Style, pick a preset and adjust the font, size and position. "Show safe area" marks where the frame is crowded on vertical or square video.
6. Click Render video, read the summary, start the render and keep the tab open. Then click Download video.
7. Press Export SRT as well, so you have an editable copy of the subtitles for next time.

Where the words come from without AI

With AI switched off, the text has to arrive some other way. The usual sources:

• A subtitle file from a translator, a client or a colleague. If it's an SRT, turning an SRT into an MP4 covers the checks worth making before you render.
• Your own typing, which suits short clips, scripted videos and anything with little speech. Adding subtitles by hand has the keyboard routine.
• Captions a platform already made. If the video is on your YouTube channel, YouTube Studio can usually download its captions as a file; cleaning up YouTube's auto captions explains the round trip.
• A script with no timings. The editor won't align pasted text with the speech, so paste it a phrase at a time as the video plays.

ASS, SSA and SBV files aren't imported, and subtitle tracks inside an MKV aren't read. Convert those to SRT first: the free Subtitle Edit reads all three, and FFmpeg converts ASS and SSA.

What free doesn't limit

The free route here isn't a trial or a lite version, so there's no counter running in the background:

Number of videos

No daily or monthly cap on renders or exports.

Length

No fixed maximum for rendering. Long files take longer and need free disk space.

Resolution

The MP4 keeps the source's resolution, frame rate and orientation, 4K included, as long as the browser can encode that size.

Branding

No watermark, logo or end card is added.

Account

Not needed for any step on this route.

What your computer does limit

Because your machine does the work, its limits become yours:

• Browser. Rendering needs Chrome or Edge 94 or later, Safari 16.4 or later, or Firefox 130 or later, on a computer. Phones and tablets can edit and export SRT or VTT, but don't count on rendering there.
• Storage and memory. Long renders are written to the browser's private storage on your disk when it's available, otherwise they must fit in memory. The summary before rendering estimates the output size; very large files can be refused if the space isn't there. Subtitling a large video file goes into the numbers.
• Time. Speed depends on your processor, the length and the resolution. The tab has to stay open, and a laptop should stay plugged in and awake.
• Connection. The page and its fonts load from the internet, so you need to be online to open the editor.

If installing software isn't an option on the computer you're using, subtitling without installing anything looks at what a locked-down browser needs.

Free, and paid for by ads

Free tools are paid for somehow. On mydubly it's advertising: visitors who haven't bought credits see ads from Adsterra in a sandboxed frame on the page, which can't read your files. Buying credits removes them for 30 days. The ads sit on the web page, not in your MP4.

When spending a little saves a lot

Typing is free but slow for a long, talk-heavy video. If you'd spend an hour transcribing a 20-minute interview, AI subtitles would cost 20 credits (2¢), and a first Google sign-in gives 100 credits; what the free credits cover has the details. If what you actually need is a separate subtitle track inside the MP4 rather than burned-in text, this editor doesn't make one; HandBrake does, as adding an SRT to an MP4 with HandBrake shows.

About the subtitle editor on this page

Opens

MP4, MOV, M4V, WebM, MKV videos your browser can decode

Subtitles from

AI (from the speech, optionally translated into one of 21 languages), an SRT or VTT file, or typing them in

You download

An MP4 with the subtitles drawn into the picture at the original resolution and frame rate, plus SRT and VTT files

Cost

Editing, styling, rendering and SRT/VTT export are free, with no account and no watermark. AI subtitles cost 1 credit per minute (5-credit minimum per video); signing in with Google gives 100 free credits and accounts get 10 free credits a day

Privacy

The video never leaves your device and is rendered in your browser. Only for AI subtitles is the audio sent, over HTTPS, and it is deleted within 30 minutes of delivery

Rendering needs

Chrome or Edge 94+, Safari 16.4+, or Firefox 130+ on a computer. Editing and SRT/VTT export work in any current browser