How to compress large videos on iPhone to save storage (HEVC, safely)

You can reclaim serious storage by compressing large iPhone videos to HEVC, and you can do it without ever losing the original if you compress, verify, then delete in that order. This guide explains the codec tradeoff (HEVC vs H.264), why it works, and a safe workflow. I'll separate the codec facts (Apple's) from how my app implements them.

How this was made: written from building Clarity's video pipeline on AVFoundation and from Apple's HEVC documentation (linked inline). Human-reviewed by me.

The codec tradeoff, explained

The reason compression saves so much comes down to the codec. HEVC (H.265) is Apple's high-efficiency video format, introduced with iOS 11. Apple's own guidance: HEVC "offers better compression than... H.264, so they use less storage space... while preserving the same visual quality", in practice roughly half the file size at similar quality (Apple Support).

Worth knowing: newer iPhones may already shoot HEVC if you've set Camera > Formats > High Efficiency (Apple Support). If your big clips were shot in the "Most Compatible" (H.264) format, converting them to HEVC is where the easy wins are. If they're already HEVC, further compression means lowering bitrate, which is a real quality tradeoff, so weigh it per clip.

The safe compress-and-verify workflow

The danger with compressing video is doing it in a way that can lose the original mid-swap. Here's the safe sequence, which is exactly how Clarity does it:

1. Estimate the savings. See how much space a clip will reclaim before you spend the processing time.
2. Re-encode to HEVC (H.264 fallback). Clarity uses AVFoundation to produce the smaller file, falling back to H.264 where needed for compatibility.
3. Create and verify a new asset. A brand-new compressed asset is created and verified as valid, the original is untouched at this stage.
4. Only then offer to delete the original. You're asked to remove the original after the replacement exists and checks out. Even then it lands in iOS Recently Deleted for 30 days, recoverable (Apple Support).

That ordering is the safety guarantee: there is never a moment where the old clip is gone and the new one isn't confirmed.

A worked example

A 3-minute 4K/60 clip in H.264 might be ~1 GB. Re-encoded to HEVC at a sensible quality, it can land near ~500 MB, about half, while looking the same on your phone. Across your ten largest clips, that's often several gigabytes back. Actual results depend on the source bitrate and the footage; that's why Clarity shows a per-clip estimate so you only compress where it pays off.

Honest limits

• It's a deliberate, not instant, job. Re-encoding is processing-heavy, and Clarity throttles under thermal or low-power conditions. For a large batch, plug in and give it a few minutes.
• Video compression is a Clarity Pro feature. The free cleanup taste won't cover a video-heavy library.
• Compression is lossy. For footage where you want maximum quality preserved forever, keep the original uncompressed.
• iCloud-only clips are analyzed from metadata/thumbnails until downloaded, and Clarity never auto-downloads over cellular.

Get Clarity

Clarity is coming to the App Store. It compresses your biggest clips to HEVC the safe way, verify first, then offer to delete. For the storage-full context, see reclaim space from large videos.

The app never deletes anything automatically; you confirm every deletion and deleted items go to iOS Recently Deleted for 30 days. Apple processes all purchases, renewals, and billing; refunds are handled by Apple via reportaproblem.apple.com.