“App not installed because the package is invalid” is a more specific message than a generic rejection. Android got as far as checking integrity and signature and stopped there: the file is not a correctly signed package. This is almost always a problem with the file, not the phone, and it can be checked quickly.
First, two minutes for diagnostics
On each app’s card we print the file’s SHA-256 and the signing certificate fingerprint — before download, on the version page. Calculate the SHA-256 of the downloaded file and compare it with the one on the card.
- The hashes don’t match — the file is corrupted or changed along the way. Read causes 1 and 2 next; you can skip the rest.
- The hashes match — the file is intact, and the issue is how you’re installing it or what you’re installing it on. Causes 3 and 4.
Many file managers on Android can calculate a hash; on a computer it’s one command. You need to compare the entire string, not just the first characters.
1. The download was interrupted or got junk appended
Cause. Our file links are temporary and last 15 minutes. If a download took longer, or a download manager tried to resume the file via an expired link, an error page gets appended to the end of the APK. Technically the file exists, and even its size looks plausible — but the signature no longer matches.
What to do. Delete the file, open the card again, and download it in one piece over Wi-Fi using the browser’s built-in downloader. Don’t resume, don’t pause for a long time, and don’t pull it through third-party accelerators.
2. The APK was modified after signing
Cause. The signature covers the entire contents of the package, and any tampering breaks it. Most often it’s not attackers who break it, but everyday tools: an archiver recompressed the zip, an “optimizer” cut out resources it deemed unnecessary, an antivirus removed a chunk, or the file was run through a service that repackaged the archive.
What to do. Take the original file and do nothing else to it between downloading and installing. Separately: don’t try to “fix” an APK with an archiver — unpacking and repacking guarantees an invalid package.
This also applies to mods and “cracked” builds from third-party sites: they are re-signed with someone else’s key, and often carelessly. We don’t publish such builds at all.
3. It’s a container, not an APK
Cause. .xapk, .apkm and .apks are archives containing a set of app parts. They don’t have their own package signature, so signature verification finds nothing meaningful in them.
What to do. Check the extension. In our catalog, 1025 out of 1030 cards serve a regular single .apk that installs with a tap; five serve .xapk — those require an installer that can unpack the container and install the parts in one installation session. Renaming doesn’t help.
4. The phone doesn’t accept this signature
Cause. APK signatures have several schemes. The old “v1” scheme signs files inside the archive; newer ones, starting with “v2,” sign the entire file. Android 11 and later refuses to install apps with a high target API if they only have the outdated v1 signature. The reverse also happens: an APK signed only with the v2 or v3 scheme won’t install on Android 6 and below, because the older system doesn’t know such schemes.
What to do. On an old phone, look for an older build — it’s almost certainly signed with the old scheme too. 363 catalog cards have more than one version, and for 49 of them the previous build requires a lower Android version than the current one; the version list opens from the app page. Ready-made selections by system version: Android 5.0, Android 6.0, Android 7.0.
An incorrect clock is a rare but real cause
A certificate has an expiration date. If the phone’s date is wrong (for example, after a full discharge), the system may decide that the signature is not yet valid or is already expired. Turn on automatic date and time detection and repeat the installation — the check takes half a minute and sometimes solves everything.
About our files — so there are no surprises
The certificate fingerprint on the card is the fingerprint of the key that signed our specific file. Measured on 09.09.2026: 965 out of 1030 cards have the same one, because those builds are assembled from parts and signed with our key; another 64 cards carry the original publisher signatures. This does not affect integrity verification — the file is correctly signed and is not considered “invalid” — but it does affect installing over a version from Google Play: there you’ll get a different error. It’s covered in the article “App not installed”.
If the message was different from “invalid package,” see “Package parsing error”, “Not supported on device” or the general checklist “APK won’t install”.
