Sources & Verification 1 of 8
Primary Sources
Primary sources define what PNG is and how a conforming PNG datastream behaves. They take priority over tutorials, software defaults, forum posts, and production conventions when the claim concerns the file format itself.
| Source | Authority | Used to verify |
|---|---|---|
| W3C PNG Specification, Third Edition: https://www.w3.org/TR/png-3/ | Current W3C Recommendation, published June 24, 2025 | Raster structure, static and animated PNG, color types, bit depths, alpha, chunks, filtering, compression, metadata, conformance, and media types |
| PNG Third Edition errata: https://www.w3.org/2025/06/REC-PNG-20250624-errata | W3C errata for the current Recommendation | Corrections or clarifications published after the Recommendation |
| PNG Implementation Report: https://w3c.github.io/png/Implementation_Report_3e/ | W3C Working Group implementation evidence | Feature implementation and interoperability evidence for the Third Edition |
| PNG public chunk and keyword register: https://www.libpng.org/pub/png/spec/register/ | PNG specification register | Registered public chunks, extensions, and text keywords |
| libpng: https://www.libpng.org/pub/png/libpng.html | Official PNG reference library | Reference decoding and encoding implementation context |
Older PNG specifications remain useful for historical and compatibility research, but this guide uses the Third Edition for current format claims unless a claim explicitly concerns an earlier version.