CRX vs ZIP

Both are the same thing, plus a wrapper

A CRX is a ZIP archive with a binary header in front of it. The archive inside is byte-for-byte identical to a normal ZIP of the same extension. Converting between them is therefore a matter of removing or adding a header, not of repackaging anything.

That framing answers most "which should I use" questions immediately: everything that happens inside the archive is unaffected, and everything that depends on the signature is.

Side by side

What you lose by converting to ZIP

One thing: the signature. It lives in the CRX header, so a converted ZIP is unsigned. In practical terms that means:

• Chrome will not auto-update an extension loaded from a converted ZIP. An unpacked extension does not auto-update anyway, but it is worth knowing that re-signing is what a published extension relies on.
• You cannot prove the ZIP came from the publisher. Anyone can produce an identical-looking ZIP. If provenance matters to you, that proof lived in the CRX.

What you do not lose: the code, the manifest, the icons, the structure. Nothing inside the archive is modified. See what a CRX file is for the byte-level detail.

When converting is the right move

• You want to read the manifest. TheManifest Viewer accepts a ZIP directly, so converting is the simplest path.
• You want to check the permissions. Same reason — open the manifest, then run it through the Permission Checker.
• You want to load it unpacked. Chrome's developer mode loads adirectory. Convert, unzip, and point it at the folder.
• You want to edit it. Changes to a CRX invalidate its signature anyway, so there is nothing to preserve by staying in that format.

When to keep the CRX

• You intend to install it, rather than inspect it.
• You need the publisher's signature to stay intact.
• You want Chrome to handle it as a normal package, updates and all.

Converting safely

Two things to be careful about, both handled by theconverter on this site:

• Treat the archive as data. Unpacked extension code is attacker-controlled by default. Nothing inside should be executed, and no HTML or JavaScript from the archive should be rendered into a page. The converter reads bytes and never evaluates them.
• Validate the paths. A malicious archive can contain entries like../../something or absolute paths, which turn extraction into a write outside the destination. The converter rejects such an archive as a whole rather than extracting part of it, because a partial extraction would no longer match the original extension.

A note on CRX versions

Chrome has used two header layouts. CRX2 stored a public key and a signature, both with explicit lengths. CRX3 replaced them with a single metadata block whose size is declared in the header. Both are simple to read, and this site's converter supports both — see the tool's limitations for exactly what that does and does not cover.