Practical guides
Practical guides
Reproducible examples that explain a tool's result, not just its buttons.
Why a large JSON integer can change
An order ID can be valid JSON yet change when an application turns it into a JavaScript Number. Formatting and calculating are different tasks. The example below uses 9007199254740993, deliberately one above the largest safe integer.
Why character counters disagree
A character limit is incomplete without a counting rule. A family emoji looks like one symbol but contains multiple code points and UTF-16 units. The examples distinguish visible grapheme clusters, JavaScript string length and UTF-8 bytes.
PNG quality: why the file size does not change
Apps24 disables the quality slider for PNG because this setting cannot reduce its file size. Its browser canvas encoder applies quality to JPEG and WebP, not PNG. To check this rather than assume it, we encoded the same synthetic gradient at two PNG qualities and compared bytes and SHA-256 hashes.
JPEG, WebP and PNG compared with a real photo
The same quality number does not mean the same result across formats. We uploaded NASA's Earthrise photograph to Apps24 and downloaded JPEG and WebP at 80% quality, with dimensions at 100%. The source and actual downloads below let you inspect and repeat the comparison.
QR margins and checks before printing
Generating an image is not proof that a printed QR will scan. We decoded two Apps24 PNG samples, a URL and Korean text, with a separate ZXing-C++ reader and inspected the clear margin in pixels.
Calibrate an online ruler and check its error
A web page cannot automatically know whether its displayed centimetre is a physical centimetre. Apps24 matches an on-screen rectangle to an object known to be 85.60 mm wide. The table verifies implementation calculations, not a physical measurement.
Apps24 checks examples against the implementation and regression tests. Browser experiments state their conditions; they do not certify every device. Report an error with the page URL, input, expected result and browser. Never send passwords, private documents or personal data.
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