What colour information survives export to PNG/web, which chunk wins when several are present, and what is assumed when an image is untagged?

PNG Third Edition (W3C Recommendation, 24 June 2025) ranks colour chunks cICP 1, iCCP 2, sRGB 3, cHRM+gAMA 4 and says the lowest number 'should' take precedence with the others ignored (decoders use the highest-precedence chunk they understand); mDCV is informative mastering-display metadata that must be accompanied by cICP; CSS Color 4 says untagged images must be treated as sRGB. Curator qualifications: Normative strength: the precedence rule uses 'should', and decoders that do not understand cICP fall back to the next chunk they understand; do not render it as an absolute 'wins'. ICC v2/v4 PCS statements (S23, E5/F2) and PNG decoder gamma section (E6) not reinspected. CSS Color 4 is a Candidate Recommendation Draft; live TR text. Specification reading only; no PNG encoded or decoded. Limitations: Specification reading only; no PNG encoded or decoded. Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

{
  "citations": [
    {
      "url": "https://www.w3.org/TR/png-3/",
      "note": "w3.org/TR/png-3 (REC 2025-06-24), section 4 colour-chunk paragraph and Table 1; section 11.3.2.7 mDCV; CSS Color 4 (TR copy fetched 2026-10-22) section on untagged images"
    },
    {
      "url": "https://www.color.org/specification/ICC.1-2022-05.pdf",
      "note": "w3.org/TR/png-3 (REC 2025-06-24), section 4 colour-chunk paragraph and Table 1; section 11.3.2.7 mDCV; CSS Color 4 (TR copy fetched 2026-10-22) section on untagged images"
    },
    {
      "url": "https://www.w3.org/TR/css-color-4/",
      "note": "w3.org/TR/png-3 (REC 2025-06-24), section 4 colour-chunk paragraph and Table 1; section 11.3.2.7 mDCV; CSS Color 4 (TR copy fetched 2026-10-22) section on untagged images"
    }
  ]
}