Overview
Add video auto captions to a clip with spoken audio and get an MP4 to review before sharing. Choose the speech language, font size, font color, and caption position, then check the words and placement against your recording. Auto Captions accepts MP4, WebM, MOV, MKV, and AVI video.
Auto Captions uses AI speech recognition to add subtitles to video. The registered result is an MP4 file.
When to use
- Use Auto Captions when your video has spoken audio and you want a captioned MP4. A silent clip does not provide speech to caption.
- Choose a different workflow if you need a separate subtitle file. Auto Captions produces MP4, not a separate subtitle-file export.
How to use
Open Auto Captions and sign in to its online workspace.
Upload one video file in MP4, WebM, MOV, MKV, or AVI format, up to 500 MB. Choose a clip with spoken audio and keep the original in case you need to return to it. Set Speech Language to Auto-Detect or choose the language spoken in the recording. Adjust Font Size, Font Color, and Position as needed; control availability may depend on the active workspace.
Choose Process Auto Captions in the workspace. When the result is ready, play the MP4 and compare the words with the recording. Check names, numbers, and overlapping speech; review caption timing, reading time, and whether captions cover important visuals. Download the MP4 after reviewing it. If text needs correction, use an editing workflow that lets you change it before publishing.
Settings reference
| Setting | Options | Default |
|---|---|---|
| Speech Language | auto: Auto-Detect en: English es: Spanish fr: French de: German it: Italian pt: Portuguese ja: Japanese ko: Korean zh: Chinese | auto |
| Font Size | 18: Small (18px) 24: Medium (24px) 32: Large (32px) 40: Extra Large (40px) | 24 |
| Font Color | white: White yellow: Yellow green: Green cyan: Cyan red: Red black: Black | white |
| Position | bottom: Bottom top: Top | bottom |
Formats & limits
| Detail | Requirement |
|---|---|
| Input formats | .mp4, .webm, .mov, .mkv, .avi |
| Output formats | MP4 |
Access & cost
| Detail | Requirement |
|---|---|
| Processing mode | Online processing requires sign-in and an internet connection. |
| Online processing | Sign-in required; Internet connection required |
Examples & use cases
A social media editor preparing an interview clip.
Caption a short interview answer
A 45-second MP4 has spoken English. The speaker’s name and pauses make it important to check the wording and timing before sharing.
.mp4 to MP4
- Speech Language:
- en
- Font Size:
- 24
- Font Color:
- white
- Position:
- bottom
- Choose English in Speech Language to match the interview.
- Use the medium Font Size, white Font Color, and bottom Position as a starting point; these controls configure caption appearance.
- Play the result and check the speaker’s name and pauses against the interview audio.
Expected outcome
A captioned MP4 to review. Compare the interview wording and caption timing with the original recording before sharing.
A small-business owner preparing a product video.
Caption a Spanish product explanation
A 90-second WebM contains spoken Spanish, and the speaker points to product details near the bottom of the frame.
.webm to MP4
- Speech Language:
- es
- Font Size:
- 32
- Font Color:
- yellow
- Position:
- top
- Choose Spanish in Speech Language to match the spoken language.
- Try Font Size 32 and yellow Font Color for a larger, differently colored caption treatment. Choose top Position because important product details are near the bottom.
- Watch the result and check the Spanish wording and whether the captions leave the product details visible.
Expected outcome
A captioned MP4 to inspect. Check the words against the speech and see whether captions leave the product details unobscured.
A team member preparing a short training recording.
Caption a Japanese training clip
A two-minute MOV contains spoken Japanese and on-screen steps near the top of the image. The captions need review before the clip is shared internally.
.mov to MP4
- Speech Language:
- ja
- Font Size:
- 24
- Font Color:
- white
- Position:
- bottom
- Choose Japanese in Speech Language to match the recording.
- Use the medium Font Size and white Font Color as a starting point. Choose bottom Position to place captions away from the on-screen steps near the top.
- Play the result and check the Japanese wording, caption timing, and visibility of the training steps.
Expected outcome
An MP4 with generated captions to review. Compare the text with the audio and check that the training steps remain visible.
More ways to use it
- A creator preparing a spoken clip for a social post.: The creator wants captions on the video and needs to check their wording and placement before publishing. A captioned MP4 to review for wording, timing, and whether captions cover important visuals. Speech Language: auto, Font Size: 24, Font Color: white, Position: bottom.
- A presenter preparing a recorded explanation.: The presenter wants captions in a supported speech language, but a later step requires a separate subtitle file. Auto Captions produces an MP4, not a separate subtitle file. Choose a workflow that explicitly offers the file type you need. Speech Language: en.
Troubleshooting
The generated captions do not match speech that is in English.
Try this: Set Speech Language to English, then process the video again.
What to expect: Speech Language is configured for English. Check the resulting words against the audio.
Captions appear over important content at the bottom of the frame.
Try this: Set Position to Top, then process and review the result.
What to expect: The Position control is set to place captions at the top. Check the MP4 to see whether that placement works for this video.
Privacy
Online processing uploads files. Completed results may remain available for later download. See Privacy Policy for current file-handling and retention details. Check the processing mode before starting.
Frequently asked questions
Should I review the captions before posting?
Yes. Play the full MP4 and compare the captions with the recording. Pay particular attention to names, numbers, and overlapping speech, then check timing, reading time, and whether captions cover important visuals. Correct errors in an editing workflow that lets you change the text before publishing.
How do I automatically add captions to a video?
Open Auto Captions, upload one supported video with spoken audio, set Speech Language and any caption appearance controls you need, then choose Process Auto Captions in the workspace. Review the resulting MP4 before using it.
Are AI-generated video captions always accurate?
Auto Captions uses AI speech recognition to add subtitles to video, but no accuracy guarantee is registered. Check the generated words against the audio, especially names, numbers, and overlapping speech, before sharing the MP4.
What video formats can I upload?
Auto Captions accepts MP4, WebM, MOV, MKV, and AVI video. Upload one video file, up to 500 MB.
What format does Auto Captions produce?
The registered output is MP4. If you need a separate subtitle file, choose a workflow that explicitly offers that file type.
Which speech languages can I select?
Speech Language offers Auto-Detect and English, Spanish, French, German, Italian, Portuguese, Japanese, Korean, and Chinese. Choose the spoken language, then review the generated words against the audio.
Can I customize caption font size, color, and position?
The controls include Font Size, Font Color, and Position. Font Size offers 18, 24, 32, or 40; Font Color offers white, yellow, green, cyan, red, or black; Position offers bottom or top. Review the MP4 to see how your choices appear.
Can I edit the generated transcript or captions in Auto Captions?
Text editing is not listed among this tool’s registered controls. If you find an error, use a caption-editing workflow that lets you change the text before publishing.
Can I export captions as an SRT or VTT file?
Auto Captions has a registered MP4 output; separate SRT and VTT exports are not listed for this tool. If you need one of those files, choose a workflow that explicitly offers that export.
Can I generate captions from an audio-only file?
No audio-only input format is listed. Auto Captions accepts MP4, WebM, MOV, MKV, and AVI video and uses speech recognition to add subtitles to video.
Can I translate captions into another language?
Speech Language configures the speech-captioning workflow; translation is not listed among this tool’s controls. Choose a separate video translation workflow if translation is your next task.
Can I use Auto Captions without signing in?
This tool runs online and requires sign-in and an internet connection. Review the processing charge shown in the workspace before starting.
How should I handle a silent video?
Choose a video with spoken audio. Auto Captions uses speech recognition to add subtitles, and a silent clip does not provide speech to caption.
Can I add animated or karaoke-style captions?
Animation and karaoke-style controls are not listed for Auto Captions. The registered appearance controls are Font Size, Font Color, and Position; review the MP4 to check how those choices look.
Are captions burned into the video or selectable?
Auto Captions produces an MP4, but the registered output details do not specify whether its captions are burned into the picture or selectable. Check the result for the format you need before sharing.
Do auto-generated captions guarantee accessibility compliance?
No accessibility-compliance guarantee is registered. Review the full MP4, compare the words with the audio, and check caption timing, reading time, and whether captions cover important visuals before publishing.