Most short videos are watched with the sound off. Without captions, a viewer scrolling past sees someone talking and no idea what they're saying. With captions, they can follow along in silence, and they're far more likely to stay.
Adding captions used to mean an editing app, a subscription for the nicer styles, or a watermark on the free version. You don't need any of that. This guide shows how to add captions to a video for free in your browser, with no watermark, using Spokly's Captions on video tool, and how to make the captions easy to read once they're on.
Burned-in captions or a subtitle file?
Before you start, decide which kind of captions you need, because there are two:
- Burned-in captions are drawn into the picture. Everyone sees them, on every platform, and they can't be turned off. This is what you want for Reels, TikToks and Shorts, and for videos you send on WhatsApp.
- A subtitle file (SRT or VTT) sits next to the video. Viewers turn it on or off, and the platform decides how it looks. This is what you want for YouTube videos, courses, and anything you'll edit further.
This guide is about burned-in captions. If you need a subtitle file instead, the Subtitle file tool makes one from the same video. For a closer look at the difference on each platform, read TikTok and Instagram auto captions vs burned-in captions.
What you need
- The video file on your phone or computer: MP4, MOV or WebM.
- A recent browser. Chrome, Edge or Safari export an MP4. Some other browsers can only save WebM, which some apps don't accept; the tool tells you up front if that's the case.
- Length: up to 90 seconds on a phone, up to 10 minutes on a computer.
There's no sign-up and nothing to install. The video is processed on your device and never uploaded.
Step by step: add captions to your video
- Open the tool and drop your video into the box, or tap it to choose a file.
- Choose the spoken language. Picking the language gives better results than Auto-detect. On a computer, choose Accurate for languages other than English; it's slower but makes fewer mistakes.
- Press Make captions. Your browser listens to the video and times every word. The first time, it downloads the free speech model once; after that it starts right away.
- Choose a style. Four styles are included, all free:
- Bold outline: white text with a thick dark outline. Readable over almost anything.
- Highlight word: the word being spoken lights up. Popular on Reels and TikTok.
- Dark box: text on a dark band. Calm and easy to read over busy footage.
- Minimal: small and clean, for videos where the picture matters most.
- Set the position, size and font. Bottom, middle or top; small, medium or large; Inter, or Cairo or Tajawal for Arabic.
- Check the captions. Tap any caption in the list to jump to it in the preview. Fix wrong words, and adjust start and end times where a caption feels early or late.
- Press Export video (MP4). The tool draws the captions onto every frame and saves a new MP4 with your original sound. There's no watermark.
That's it: the file is ready to post. If you want the captions as text too, you can also download them as an SRT or VTT file from the same screen.
Choosing a style that's easy to read
Captions only help if people can read them in the second or two they're on screen. A few rules of thumb:
- Contrast beats decoration. White text with a dark outline or a dark box works on bright skies, busy streets and dark rooms alike. Thin text without an outline disappears over light backgrounds.
- Use one style per video. Switching styles halfway through looks like a mistake.
- Size for a phone. Most viewers watch on a phone held at arm's length. If the text looks a little big on your computer screen, it's probably right on a phone.
- Highlighting helps people follow. The Highlight word style shows where the speaker is in the sentence. It's especially good for fast talkers.
Where to place captions
On TikTok, Instagram Reels and YouTube Shorts, the app covers parts of your video: buttons on the right side, and your username, post text and music at the bottom. Captions placed at the very bottom of the frame can end up hidden behind them.
- Bottom position works well for horizontal videos and for platforms without overlays.
- Middle position is the safest for vertical videos on TikTok and Reels: it stays clear of the app's buttons and text, and it's where viewers are already looking.
- Top position suits videos where the speaker's face fills the lower half, or where on-screen text is already at the bottom.
When in doubt, export once, send the video to your own phone, and look at it inside the app you're posting to.
Reading speed and caption length
Spokly's captions appear a few words at a time, which is easier to read on a phone than full sentences. Even so, check two things:
- Each caption should be on screen long enough to read. If you can't read a caption before it disappears, extend its end time a little, or split the words across two captions.
- Keep it to two short lines. Longer captions cover the picture and are hard to read at a glance.
Fast speakers and lists of numbers are where captions get crowded. A quick pass through the caption list catches most of it.
Fixing mistakes before you export
Automatic captions are good, but not perfect. Before exporting, read through the list once and look for:
- Names, brands and places. Speech models often mishear words they haven't seen much.
- Numbers and prices. "Fifteen" and "fifty" sound alike; check them against what was said.
- Words in another language. If the speaker switches languages, the captions may struggle in that part. Fix those captions by hand.
- Filler words. You can delete "um" and "uh" from a caption to make it cleaner; the timing stays as it was.
Captions in Arabic and other right-to-left languages
Arabic captions are laid out right to left, with the Cairo and Tajawal fonts made for Arabic script. Choose your dialect as the spoken language: Egyptian, Gulf, Levantine and others are on the list. On-device Arabic recognition may need a few more fixes than English, so read the captions through before you export.
Posting your captioned video
The exported MP4 works like any other video file:
- TikTok, Reels and Shorts: upload it as usual. Turn off the platform's own auto captions for this video, or viewers may see the words twice.
- WhatsApp and email: send the file directly; the captions are part of the picture.
- LinkedIn and Facebook: upload the MP4. If you also want a caption track people can switch off, upload an SRT file as well; here's how to make an SRT file from a video.
AI tools for writing posts and translated captions are coming soon to Spokly; captions on video stay free.
FAQ
Is there really no watermark?
No watermark. The exported MP4 contains your video, your original sound and the captions you chose, nothing else.
Is my video uploaded anywhere?
No. The speech recognition and the export both run in your browser, so the video stays on your phone or computer.
Why is my export a WebM file instead of an MP4?
Some browsers can only save video as WebM. Use Chrome, Edge or Safari to get an MP4, which every social platform accepts. The tool tells you before you start if your browser can only save WebM.
Can I add captions to a long video?
Up to 10 minutes on a computer and 90 seconds on a phone. For longer videos, make a subtitle file instead and upload it to the platform, or split the video into parts.