Copsy›Avoid corrupted footage

How to avoid corrupted footage — and catch a bad copy before you wipe the card

Written by a working DIT · Copsy · Last verified June 2026

Short answer

Corrupted footage comes from two places: damage in-camera (yanking a card mid-write, a dying battery, a failing or cheap card) and a bad copy (interrupted transfer, flaky reader, a drag-and-drop that silently dropped bytes). You avoid it with habits: finish writing before ejecting, use good cards, never interrupt a copy, keep redundant copies. And one rule sits above all of them: verify every copy with checksums before you format the card.

Copsy automates that last part. It copies the card to a drive (and optionally Google Drive or Dropbox in parallel), verifies every file with ASC-MHL checksums, and keeps you from wiping a card that didn't verify. It can't repair a file that was already damaged in-camera. That's exactly why you keep more than one copy.

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What "corrupted footage" actually means

"Corrupted" gets used for two very different problems, and confusing them is how people lose footage for good. The first is in-camera damage: the file on the card was never written completely or correctly. The second is copy-stage corruption: the original on the card is fine, but the copy you made of it isn't a faithful, bit-for-bit duplicate. Knowing which one you're dealing with tells you both what's recoverable and what habits would have prevented it.

Why footage gets corrupted

Most lost clips trace back to one of these causes. None of them are exotic. They're the everyday mistakes that happen at the end of a long shoot day.

Pulling a card mid-write. If you eject (or the camera loses power) while a clip is still being written, that clip can be left truncated or unreadable. Cameras buffer; the "recording stopped" light isn't always the moment the card is finished.
Failing, worn-out, or counterfeit cards. Flash memory degrades. A card that's thousands of formats deep, or a cheap counterfeit bought from a marketplace listing, can drop blocks silently. If it has ever thrown an error, retire it.
Interrupted copies. A transfer that gets cut off (unplugging the drive, closing the laptop, a cable that wiggles loose, a reader that drops the connection) can leave a partial file that looks like it copied but didn't.
Unverified copies. A plain Finder drag-and-drop can finish "successfully" while quietly dropping or mangling bytes, especially over a flaky USB hub. Nothing tells you. You only find out when you scrub into the clip in the edit, long after the card is gone.
Formatting the card too early. The single most expensive mistake: wiping the source before you've confirmed the copy is good. Now there's no original left to fall back on.

The habits that prevent it

Avoiding corrupted footage is mostly discipline, not gear. Do these in order, every card, every time.

Let the card finish writing, then eject properly. Stop recording, wait a beat, power down or eject cleanly. Don't yank a card out of a hot camera.
Use quality cards and retire bad ones. Buy from real retailers, not random marketplace sellers. Any card that has errored once is suspect, so pull it from the kit.
Never interrupt a copy. Once an offload starts, leave the drive, reader, and cable alone until it's done. Use a reliable reader and a solid cable, not the cheapest one in the bag.
Keep redundant copies. At least two, on separate drives, ideally following a 3-2-1 approach (a working copy, a backup, and one off-site or in the cloud). Copsy can copy to a drive and to Google Drive or Dropbox in parallel from the same offload.
Verify every copy with checksums before you format. This is the one that turns "I think it copied" into "I know it copied bit-for-bit." Do not wipe the card until this passes.

The one rule: verify before you format

A copy that finished and a copy that's correct are two different things. Checksum verification hashes the source and the copy and compares them, so if a single byte is off, you know before the original is gone. Copsy verifies every file with ASC-MHL (the same media-manifest standard used on film sets and for Netflix deliverables), writes a manifest alongside the footage, and treats a card as safe to format only after verification passes. Format after the green light, never before.

How Copsy catches a bad copy early

Copsy is built around the assumption that a copy can go wrong, so it checks every one. Here's what it does on each card, and, honestly, what it doesn't do.

Detects the card by content. Plug in an SD, CFexpress, camera, drone, or audio card and Copsy recognizes the source (Sony, ARRI, RED, Blackmagic/BMD, Canon, drones, audio recorders) instead of treating it as a nameless folder.
Copies to a drive, and a cloud in parallel. An external drive plus optionally Google Drive or Dropbox at the same time (one cloud destination at a time), organized by date and source.
Verifies every file with ASC-MHL checksums. Each file is hashed and compared against the original. A copy that didn't land bit-for-bit is flagged immediately, not weeks later in your timeline.
Keeps you from wiping an un-verified card. Verification is the gate. If it didn't pass, you haven't lost your safety net by formatting too soon.
Pings you on Telegram when it's done. So you can walk away and still know the card verified clean.

What Copsy can't do, said plainly: it cannot repair a file that was already damaged inside the camera. If a clip was written incompletely on the card, Copsy will faithfully copy and verify exactly what's there, including the damage. That's why redundant copies matter: verification protects the copy; multiple copies protect against the original being bad. Copsy is also macOS-only (macOS 13+), with no LTO/LTFS archiving and no NLE panel integration. It's a verified offload tool, not a repair or asset-management suite.

If a clip is already corrupted

If the damage happened in-camera, no offload tool can rebuild missing data. Your best options are: pull from a second card or a redundant copy if you kept one; for some camera formats, dedicated clip-repair utilities can sometimes salvage a partially written file; and if it was a one-of-a-kind take, a specialist data-recovery service is the last resort. The cheaper insurance is upstream: verified copies and at least one redundant backup, so "the file is corrupted" never means "the only copy is corrupted."

Frequently asked questions

Why does footage get corrupted?

Footage usually gets corrupted at one of two stages. In-camera: pulling a card while it's still writing, a battery dying mid-record, or a failing or cheap counterfeit card can leave a clip incomplete. At copy time: an interrupted transfer, a flaky cable or reader, or a drag-and-drop copy that silently dropped bytes can produce a file that looks fine but isn't a bit-for-bit match of the original. The dangerous part is when you format the card before confirming the copy actually landed.

How do I prevent corrupted footage?

Build a few habits: stop recording and let the card finish writing before you eject; use quality cards from real retailers and retire ones that throw errors; never interrupt a copy mid-transfer; keep at least two copies on separate drives; and verify every copy with checksums before you format the card. Copsy automates the last steps. It copies the card to a drive (and optionally Google Drive or Dropbox in parallel), verifies every file with ASC-MHL checksums, and only then is it safe to wipe the card.

How do I know if a video file is corrupted?

A corrupted clip may refuse to open, stop partway, show blocky artifacts, glitch the audio, or report the wrong duration. But some corruption is invisible until you scrub deep into a clip in the edit, long after the card is gone. The reliable check is a checksum: Copsy hashes each file as it copies and compares it against the source with ASC-MHL, so a copy that didn't land bit-for-bit is flagged immediately, not weeks later in your NLE.

Can Copsy recover corrupted footage?

No. Copsy is an offload and verification tool, not a repair tool. If a file was already damaged in-camera, Copsy cannot rebuild it. What Copsy does is prevent copy-stage corruption: it verifies every file with ASC-MHL checksums so a bad copy is caught before you trust it, and it stops you from wiping an un-verified card. That, plus keeping redundant copies, is how you avoid the situation where there's nothing left to recover from.

Is Copsy free?

Yes, Copsy is free to download and use today, with no card limit and no account required. It runs on macOS 13 or later.

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