Hash Generator
v1.3.2
MD5, SHA and HMAC digests for text and multi-gigabyte files, with a history you can undo. It's the most-installed app in the catalogue.
The hard part: keeping a pure, dependency-free hashing engine testable while the
app grew file hashing, undo, a GDPR consent flow, push and an iOS port. The App Store
screenshot pass found a real bug: a long hash ran under the previous file's name.
It was fixed for both platforms the same evening.
170 tests6 languages
10,000+ installsiOS soon
JWT Decoder
v1.0.0
Decode, inspect and verify JSON Web Tokens without the token ever leaving the phone.
The hard part: offline signature verification for 13 algorithms (HS, RS, PS,
ES and ES256K), with keys from PEM, JWK or a whole JWKS. The crypto is tested against
OpenSSL-generated vectors rather than against itself. That's how a PSS salt-length mismatch
was caught before release.
315 tests10 languagesOffline crypto
JSON Formatter
v1.0.0
Format, validate and explore JSON without silently rewriting the document you pasted in.
The hard part: it does not use json.decode, which turns
1e5 into 100000.0, drops digits from big integers and loses
duplicate keys. Instead it ships a hand-written parser. That parser keeps every number as
literal text, reports duplicate keys, and returns error codes with line and column.
266 tests10 languagesOwn parser
Chmod Calculator
v1.0.0
Octal, symbolic and ls -l permissions as views of one 12-bit value.
The hard part: a 45,824-case differential test against both GNU
coreutils and macOS chmod, with zero mismatches. Probing the real tools first
turned up five commands where the two disagree. One is chmod 755 dir, which
does not clear setgid.
244 testsDifferentialGNU + BSD
APK Analyzer
v1.0.2
Permissions, signing, components, DEX, native libraries and 16 KB readiness for any APK or AAB.
The hard part: every format is parsed in pure Dart: ZIP, binary XML,
resources.arsc, protobuf manifests, DEX and ELF. The parsers are gated by a
differential against Google's aapt2 and the NDK's llvm-readelf. That gate
passed on its first run.
70 testsaapt2 differentialKotlin bridge
PDF Toolkit
v1.0.1
Merge, split, reorder, rotate, stamp, lock and unlock PDFs on the device.
The hard part: a Kotlin engine over PdfBox, checked by a 1,107-check gate.
The gate runs every operation on a 14-file corpus and verifies the output with qpdf,
poppler and mutool. The corpus includes AES and RC4 encryption, object streams and broken
files. Rendering the outputs caught watermarks drawn in the wrong corner on rotated pages.
110 tests+1,107 output checks15 languages
Winmail Viewer
v1.0.2
Open winmail.dat, Outlook MSG, EML and MHT files, parsed entirely on the device.
The hard part: four parsers written from scratch: TNEF, Compound File/MSG, MIME and
LZFu-compressed RTF. Each is tested against a reference implementation using fixtures from
hand-written writers. Remote content is blocked by default. The app has its own
Kotlin and Swift file bridges.
79 tests4 owned parsersiOS soon
Petrol Price Pakistan
v2.1.3
Today's fuel prices, price history, a fill-up log, trip costs and a home-screen widget.
The hard part: telling the truth about freshness. Firestore answers from its own
offline cache, so the app said "Updated just now" in airplane mode. The fix gave
the app's own cache ownership of offline. Prices now come from an hourly automated
publisher. It refuses zero prices and suspicious jumps before anything reaches users.
108 testsEnglish + Urdu
1,000+ installsiOS soon
BMI Calculator
v2.0.0
Adult BMI, plus CDC BMI-for-age percentiles for children from 2 to 20.
The hard part: the old version asked for age and sex, then ignored both. It scored a
healthy 8-year-old as "severe thinness". The rewrite uses the CDC's extended
growth data. The CDC's own published percentile columns serve as the test oracle, and all
438 rows are rebuilt to the printed digit.
109 tests15 languagesCDC data
Qibla Compass
v1.1.0
Qibla direction, prayer times, manual location and a map, accurate without a network.
The hard part: no compass plugin exposes magnetic declination or sensor accuracy.
So the app ships its own heading plugin in Kotlin and Swift. A device pass also
caught every prayer time rendering in UTC. The timezone package never detects the device
zone, and 121 passing tests hadn't noticed.
151 tests15 languagesSensors
Regex Tester
v1.0.0
Test, explain and debug regular expressions, with group positions and error carets.
The hard part: Dart's RegExp exposes no group names, no error offsets
and no group positions. Those facts were measured, not assumed. So the app parses patterns
itself. A pattern with runaway backtracking runs in an isolate that can be killed, so it
can't freeze the app.
306 testsOwn parserIsolates
Shade Shift
v1.0.0
Spot the one tile with a different shade, against the clock, with a daily challenge.
The hard part: difficulty is a target CIE76 ΔE per level, reached by
bisection, so level 40 is harder than level 20 on any screen. The daily challenge needs no
server. The date seeds a PRNG that is pinned in the app, so it can't drift between releases.
195 testsColour scienceOffline