UnHEIClocal image lab
About the lab

Correctness is a product feature.

UnHEIC is a browser-local image workbench focused on a narrow promise: inspect files honestly, convert HEIC photos within explicit limits, and verify the result before offering it for download.

01

Evidence over extension

Detection begins with bounded binary signatures. A filename and browser-supplied MIME are reported as claims, not accepted as proof.

02

A declared output contract

An output is complete only when its signature, Blob MIME, filename extension and browser decode agree.

03

Local, with boundaries

File bytes stay in page memory during the workflow, while ordinary site assets and privacy-safe analytics still use network requests.

04

Limits before a crash

Compressed size is not enough. Admission estimates decoded pixels, decoder overhead, previews, output and archive duplication.

What the browser can and cannot prove

HEIC decoding is performed by the installed heic2any Worker/WASM path. That library explicitly does not copy source metadata. UnHEIC therefore reports EXIF, GPS, capture date and embedded color-profile preservation as unavailable, rather than presenting a control that cannot work.

The preview and output use decoder-rendered pixels. Manual rotation and flipping are deterministic and tested. Automatic orientation across every HEIC producer is not represented as universally guaranteed; the preview is the user-visible check before download.

How correctness is tested

The detector and conversion contracts are exercised with valid, renamed, truncated, zero-byte, animated, multi-image, brand-specific, polyglot and adversarial declarations. The fixture corpus documents expected outcomes and provenance.

Route contracts also keep canonicals, redirects, robots and the sitemap aligned. A capability that cannot produce the advertised bytes is redirected, made non-indexable, or removed.

What UnHEIC is not

  • It is not cloud storage, a sharing host, or a server conversion API.
  • It does not promise unlimited batch sizes or a conversion time independent of the device.
  • It does not preserve source metadata with the current HEIC decoder.
  • Photo-to-PDF creates raster pages; it does not perform OCR or create selectable text.
  • The format detector identifies supported signatures; unknown remains a valid result.

Want to verify the boundary yourself?

Follow the Network-panel procedure with a local test file.

Open verification guide