The extension will install without checking the CRX header. You have effectively bypassed the “invalid header” error by unpacking the extension.
This is not an IDM bug — it's a browser security change. Chromium deprecated CRX v2 headers in favor of v3, and direct sideloading is now blocked. idm crx header invalid
Before we fix the issue, we must address a common pitfall. The extension will install without checking the CRX header
: Chrome no longer supports CRX2 headers; extensions must be in CRX3 format. File Corruption IDMGCExt.crx idm crx header invalid
There are three primary reasons this error occurs with IDM specifically: