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Feature · Move & protect

Checksums, split and combine

Hash a file on demand (CRC-32, MD5, SHA-1, SHA-256) with paste-to-verify, export and verify checksum manifests, split a large file into volumes that rejoin.

Default shortcut: Alt+Enter Updated 15 August 2026 View as Markdown

Sometimes you need to prove that a file is what it claims to be — a download against a published hash, a backup against the original, a set of volumes against the file they came from. cwdio does the hashing in its host process, streams so a multi-gigabyte file never sits in memory, and reports what it found.

What it does

  • On-demand checksum in Properties. Alt+Enter on a single file shows a Checksum section: choose CRC-32, MD5, SHA-1 or SHA-256, click Compute, copy the digest — or paste the expected hash and get a ✓ / ✗ verdict on the spot. Works on files inside archives and on SFTP servers, because it hashes through the same provider that lists them.
  • Export checksums. File ▸ Export checksums… hashes the selection (folders recursed) into a manifest — .sfv, .md5, .sha1 or .sha256 — with a live Hashing… N files line and cancel, then a review step before the file is saved.
  • Verify checksums. File ▸ Verify checksums… on a manifest re-hashes every referenced file and shows a verdict: all matched, or per-status counts plus the list of changed and missing files.
  • Split a large file. File ▸ Split file… writes fixed-size numbered volumes, streaming the source across them at byte boundaries. Combine volumes detects the whole set from any one part and rejoins it.
  • Verified copies, elsewhere. The transfer queue can CRC-check every copy as it goes; see Transfers and the queue.

How to use it

  1. To check a download: select it, Alt+Enter, pick SHA-256, Compute, paste the line from SHA256SUMS.txt. Green tick, done. (cwdio’s own releases publish exactly such a file.)
  2. To fingerprint a folder before archiving it: select it, File ▸ Export checksums…, choose SHA-256, save folder.sha256 beside it. Years later, File ▸ Verify checksums… on that manifest tells you whether every file is still intact.
  3. To move a 6 GB image over a FAT32 stick: File ▸ Split file…, enter a custom 4000 MB, copy the parts, then select .001 on the other machine and run Combine volumes.

Details

  • Manifests use the conventional hash *path layout, with a comment header; SFV carries CRC-32.
  • Verify infers the algorithm from the hash width (8, 32, 40 or 64 hex characters), so a renamed manifest still works.
  • Everything streams and everything can be cancelled from its progress line, except that closing Properties during a multi-gigabyte hash lets it finish in the background rather than aborting.

What it deliberately does not do

  • Properties hashes one file. There is no single digest for a folder or a multi-selection — use the manifest export, which is the right tool for that.
  • Split and combine are local-only; an SFTP source is not split in place.
  • Combine has no progress line yet, and always writes beside the volumes.

Questions

How do I check a download against its published hash?

Select the file, press Alt+Enter for Properties, pick the digest in the Checksum section (SHA-256 for most releases) and click Compute. Paste the publisher's hash — or a whole line from their manifest — into the field that appears and you get an instant ✓ Match or ✗ No match. The hash is computed in cwdio's host process; only the digest travels to the window.

Which manifest formats are supported?

Export writes CRC-32 (.sfv), MD5, SHA-1 and SHA-256 manifests in the conventional hash *path form. Verify reads any of them; the algorithm is inferred from the hash width, so a renamed manifest still verifies, and SFV comment lines are skipped. Files are resolved relative to the manifest's own folder.

Does verify tell me which files changed?

Yes. The report gives exact counts of ok, mismatched, missing and unreadable files and a bounded list of the changed and missing ones, so a corrupted backup names its casualties rather than just failing.

How does split decide the volume size?

You pick it in the Split dialog — presets from 10 MB up to 4.4 GB, or a custom number of megabytes. Volumes are named name.ext.001, .002 and so on. Combine runs on any one volume, requires the run to be contiguous — a missing middle part fails loudly instead of concatenating a corrupt file — and refuses to overwrite an existing target.