Add Subtitles to an iPhone Video

What an iPhone puts in the file

A clip straight from the Camera app is usually a .MOV file holding HEVC picture (also called H.265) and AAC sound. HEVC comes from the "High Efficiency" choice under Settings, Camera, Formats. Switching that menu to "Most Compatible" makes the camera record H.264 instead, which costs more storage on the phone but opens in every desktop browser. Three other properties travel with the file and matter later:

HDR

Recent iPhones record HDR video unless "HDR Video" is switched off in the camera's Record Video settings. It is 10-bit footage meant to be shown brighter than normal video.

Rotation

The phone often stores the picture the way the sensor sees it and adds a note saying how to turn it, so an upright clip can be sideways pixels plus a rotate instruction.

Frame rate

You pick 24, 30 or 60 frames per second, and the spacing between frames can wander a little, which is normal for phone footage.

None of these changes how subtitles are written, but each one affects whether the file opens and how the subtitled copy looks. The codec side is covered in HEVC compatibility and H.264 vs H.265; the MOV container in general is on adding subtitles to MOV files.

Moving the original off the phone

Rendering is built for a desktop browser, so the first job is getting the file onto a Mac or PC without it being squeezed on the way.

• AirDrop to a Mac sends the clip as it was recorded.
• iCloud Photos works too: download the original from the Photos app on a Mac or from iCloud on the web.
• With a cable to a Windows PC, the clip sits in the phone's DCIM folder. The iPhone setting Photos, "Transfer to Mac or PC" decides what you get: Automatic converts videos to a more compatible format while copying, Keep Originals copies the HEVC file untouched.
• Sending the clip to yourself through a messaging app or email usually compresses it, and subtitles drawn on a softened picture look no better than the picture.

Live Photos are a special case: the movement is a short clip attached to a still image, not a separate video file. In recent iOS versions you can open it in Photos, tap Share and choose Save as Video, then copy that video across. Expect only a few seconds of footage.

If the phone is all you have, the editor still opens in a mobile browser for writing and fixing lines and exporting SRT or VTT, but don't count on rendering the finished MP4 there. The Mac guide and the Windows guide cover the computer side.

Will your browser decode HEVC?

When you choose a file, the editor asks the browser whether it can decode the picture. If it can't, the bar above the preview reads "Can't render this file" and the message underneath says the browser can't decode HEVC video and suggests converting to MP4 (H.264) first. Support depends on the browser and on the computer underneath it, so take the following as a general picture rather than a promise:

Safari on a Mac

Normally decodes HEVC, because macOS supports it. Rendering needs Safari 16.4 or later.

Chrome or Edge

Usually decode HEVC when the graphics hardware can; older or low-power machines may not. On Windows, system codec support can also play a part.

Firefox

HEVC support came later and varies more by system and version. If it refuses, try another browser before converting anything.

If no browser on your computer will take the clip, convert it to H.264 with a desktop converter such as HandBrake, and set future recordings to Most Compatible. Changing the extension from .mov to .mp4, or rewrapping the file without re-encoding, leaves HEVC inside and won't help; the picture itself has to be re-encoded.

Subtitling an iPhone clip, step by step

1. Copy the clip to your computer and open this page in Safari, Chrome, Edge or Firefox.
2. Drop the MOV or MP4 onto the editor. Once the browser has read it, the bar above the preview shows its size and frame rate; an upright clip shows its upright size, such as 1080×1920.
3. Choose where the words come from: "Write the subtitles automatically with AI" (Google sign-in, 1 credit per minute of video), Import SRT / VTT, or typing with Enter at the playhead.
4. Play it through and correct words and timing. Audio recorded at arm's length picks up room echo and wind, so listen closely to outdoor or distant passages.
5. Open Style. Social Media or Creator suit an upright clip; Classic or YouTube read well on a landscape one. Tick "Show safe area" to see the margins for the clip's shape.
6. Click Render video and read the summary: resolution, frame rate, output codec and bitrate, plus a note if the clip is HDR.
7. Start the render, keep the tab open, then click Download video to save the copy ending in -subtitled.mp4.

HDR, rotation and timing in the subtitled copy

The output is always standard dynamic range. When the editor detects an HDR source it warns before rendering that the subtitled copy will be SDR and colours may look slightly different. On an HDR screen, bright highlights lose some punch and skies or skin can shift a little; the subtitles are unaffected. If the HDR look matters, turn HDR Video off for clips you plan to subtitle, or grade to SDR in a video editor first so you control the conversion.

Rotation is applied to the pixels. The editor reads the iPhone's rotation note, lays out the subtitles on the upright picture and writes frames that are already the right way up, so even players that ignore rotation notes show the clip correctly.

Frame timing is carried over unchanged. The summary shows an average frame rate, but every frame keeps its original timestamp, and subtitles are placed by time rather than by counting frames, so a clip with uneven frame spacing stays in sync. Variable frame rate explains why phones record this way. The AAC sound from the Camera app is copied into the MP4 without re-encoding.

Upright clips and where they end up

Most iPhone footage for Reels, TikTok or Shorts is filmed upright, and a narrow frame holds far less text per line. The editor keeps the clip's shape and resolution and never crops it. Subtitles for vertical video deals with line length and placement in a 9:16 frame, and the pages on Instagram Reels and TikTok map where each app draws its buttons. A clip filmed in 4K renders in 4K; subtitling 4K video covers what that means for file size and disk space.

Getting it back onto the phone

The subtitled file is an MP4, normally H.264, which Photos and messaging apps accept. It is often bigger than the HEVC original, partly because H.264 needs more data for the same picture and partly because the editor sets the bitrate on the generous side. AirDrop it back to the phone, or put it in iCloud Drive and save it to Photos from the Files app. Keep the original clip and an exported SRT as your editable master: changing a word later means reopening those two, not re-subtitling the subtitled copy. If you only need a subtitle file and no video, the AI subtitle generator gets you there with fewer steps.

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