Methodology
FreeToolsPro processes tool inputs on the device using browser APIs. This page describes how results are produced and what our checks can establish.
Calculator methods
Each calculator displays its formula and assumptions. Arithmetic uses JavaScript numbers, with display rounding up to four decimal places. Full intermediate values are used until formatting. Binary floating-point arithmetic is not a substitute for a ledger requiring exact decimal accounting.
Business days use UTC calendar dates, configurable weekends and only the holidays entered by the user. No national holiday feed or financial rate feed is used.
Image processing
File headers are parsed before image decoding to inspect dimensions, animation and selected metadata containers. Compressed file size alone does not describe the memory needed to decode an image. A 4,000 × 3,000 image needs roughly 48 MB for one uncompressed RGBA pixel buffer, before additional browser allocations.
Where supported, image processing runs in a Web Worker with ImageBitmap and OffscreenCanvas. A feature-detected canvas fallback is available. Every requested output format is checked against the Blob type returned by the browser.
| Constraint | Desktop | Touch / low-memory device |
|---|---|---|
| Input file size | 25 MiB | 12 MiB |
| Decoded pixels | 32 megapixels | 12 megapixels |
| Maximum side | 8,192 pixels | 8,192 pixels |
1 KB is 1,000 bytes. 1 MiB is 1,048,576 bytes. Exact-KB mode searches quality and may reduce dimensions to stay under the cap. It reports when the result falls below the tolerance band. It does not pad outputs or promise lossless compression.
Data transformations
UTF-8 conversion uses TextEncoder and a strict TextDecoder. SHA digests use Web Crypto. UUIDs follow the RFC 9562 version and variant layout using cryptographically secure random bytes. CSV conversion preserves cell values as strings and rejects inconsistent row widths or duplicate headers.
Testing and reproducibility
The source package includes fixed calculator vectors, malformed-input cases, developer transformations, image header and size-search tests, tiny fixtures and a browser test harness. The deployment package includes the actual build and test reports. A successful automated check is evidence for the tested case, not a guarantee for every file or device.
Browser codec output can vary by browser, operating system and version. Compare achieved sizes and previews on your target device. No live browser-performance comparison or field Core Web Vitals claim is published without measured data.
Privacy and quality boundaries
No remote-file URL importer, processing API, database or account is part of the launch tools. Analytics uses an allowlist of coarse events and starts disabled. Developer tokens and input content never enter its event payloads.
See individual tool pages for worked examples and specific limits. Methodology last reviewed 2026-09-09.