How to Compress a Video on iPhone
Start with the job you need to finish: remove unwanted footage, make the entire clip smaller, or meet a specific upload limit. Those are different tasks, so one setting will not solve all three.
Reviewed
Choose the right method
Keep the original until you have played the new copy and checked its size. A smaller file can lose detail; no method guarantees the same reduction for every video.
1. Trim seconds you do not need
When only part of a clip matters, shorten it before reducing picture quality. In Photos, open the video, choose Edit, and move the two timeline ends to the part you need. Preview the selection, finish the edit, and choose Save Video as New Clip to keep both versions.
Trimming changes duration; it does not let you select a precise megabyte limit. A useful review clip might need only the action and a little context, not the long pause before it. Check the new file rather than assuming it is now small enough.
Apple’s trimming instructions explain the save options and how they differ.
2. Export at a lower resolution in iMovie
For a full-length clip without a strict size ceiling, iMovie offers a local export workflow. Apple’s current instructions describe iPhone 12 or later with iOS 26 or later; earlier devices and versions may show different steps or options.
- In iMovie, start a new Movie project, select the video from your library, and create the movie.
- Finish editing, open the share controls, then choose the video-sharing option and Options.
- Choose a lower available resolution. Save a separate file, then compare its detail and size with the source.
A lower-resolution export is not a fixed-size target. Small writing, faces and movement need different amounts of detail. Do not repeatedly export an already compressed copy: return to the original when trying a different setting.
Source: Apple: compress a video on iPhone.
3. Use a maximum file size when a form requires one
For a known upload ceiling, use the existing 25MB video compressor, or choose a different target in the tool. For mailbox-specific advice, read the email compression preset before selecting a limit.
- Open the tool in your browser and choose a video you are authorised to process. The file must be available to the browser; a cloud-only item may need downloading first.
- Read any file or memory warning, set a maximum below the recipient’s limit, and start compression. The first run also needs to load the media engine.
- Keep the page open while it works. If you cancel or change the file or output settings, do not expect the old result to remain usable.
- Download the completed copy and play it outside the page before sharing. Confirm that its sound, duration and important details are present.
VidSlim uses decimal MB: a 25MB target means a maximum of 25,000,000 bytes, not an exact output size. An encoded result can be smaller. Targets too small to preserve source audio are rejected rather than silently dropping the sound.
Long clips can become soft at a small target. When the limit is optional, try quality-first compression or send an approved sharing link instead. VidSlim does not send mail or upload the video to your cloud account.
Check the saved file, not just the completion message
For a copy in Photos, open its information view to inspect the file size. In Files, locate the saved copy and check the size shown with it. Open that exact copy and listen to the beginning and end; compare small text and a section with movement. A download click alone does not prove the file was saved where you expected.
Save to a location you can find again. Apple’s iMovie file-sharing guide distinguishes the photo library, on-device storage and iCloud Drive. Cloud syncing depends on your settings, so local encoding is not a promise that every later save remains off the cloud.
When to stop and choose another route
- The browser reloads or reports a memory limit
- Try a shorter source or move the task to a computer. Do not keep retrying an oversized file; browser memory and device limits still apply.
- A MOV, HEVC or HDR source behaves differently
- A filename extension does not guarantee codec or colour compatibility. Use a compatible export from an editor, then check the copy. This guide does not claim that every iPhone camera format preserves its original appearance in every browser.
- The file is small enough but the recipient still rejects it
- Check the format, total message size and the organisation’s policy. A file-size target is not a guarantee of email delivery or acceptance by every upload form.
For your next recording
Review the resolution and frame rate in the camera settings before recording a new clip. Changing a camera setting does not change videos you already recorded. A smaller capture setting can be useful for a quick message, but keep enough detail for the actual task.
Apple’s recording-settings reference describes options that vary by model.