Troubleshooting

APK Won’t Install on Android: Match the Error, Then Fix It

The error message tells you which of five causes you have. Match it first, then fix it, because re-downloading rarely helps.

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The error message is the diagnosis

Five causes, one message each. Fix the one your message names rather than all five.
MessageCauseFix
App not installedSignature conflict with an existing packageUninstall the existing copy, then install again
There was a problem parsing the packageTruncated or incomplete downloadRe-download the file completely
Not enough spaceInsufficient storage for three times the file sizeFree space, then retry
App blocked by Play ProtectThe system scanner flagged the fileDecide deliberately; do not simply override
App not compatibleMinimum version or architecture mismatchThe device cannot run this build
Install cancelledUnknown sources not allowed for this appEnable the permission and retry

Why a signature conflict looks like a corrupt file

Android will not replace an installed package with one signed by a different key. When it refuses, the download has already completed, so it is tempting to blame the file and download it again. Doing that repeats the same conflict. The message is telling you the file is fine and the package already present is the obstacle.

How to work through an install failure

  1. 1.Read the error and match it above

    The message narrows five possibilities to one, which is faster than trying fixes at random.

  2. 2.Check that unknown sources is allowed

    A build can only install if the setting permits installation from unknown sources for the app doing the installing.

  3. 3.Free the storage three times the file size

    Android needs the download, the extracted install and the optimised code to coexist while installation completes.

  4. 4.Uninstall a conflicting package, then retry

    A differently-signed copy already present is the usual cause of a repeated refusal rather than a damaged download.

When re-downloading helps and when it does not

Frequently asked questions

Why does it say app not installed?
Usually a signature conflict: an existing copy signed by a different key cannot be replaced by this file, so the install stops after the download completes.
What does parsing the package mean?
The file is incomplete or not a valid package, which almost always means the download was truncated rather than that the app is faulty.
Why does it fail with plenty of space?
Android needs roughly three times the file size free, because the download, the install and the optimised code exist together during installation.
Does re-downloading help?
Only for a parsing error. Signature, storage and compatibility failures return unchanged, so match the message before repeating the download.

Worth knowing: "App not installed" after a completed download is almost always a signature conflict with an existing package, not a corrupt file.