pypi / idna

idna

What changed in idna 3, from its official release notes, upgrade guides and advisories. Sources checked 2026-10-17.

5 breaking2 security1 deprecations2 new APIs and options1 performance1 behavior and defaults2 fixes and other

See which of these apply to your code, ranked, in your agent:

npx @unstale/cli init

idna 314 changes

Reject A-labels that are not the canonical Punycode encoding of their U-label.
3.19release notes
The deprecated transitional argument is now completely ignored.
3.19release notes
Label helper functions and the incremental codec consistently raise IDNAError for empty labels and non-ASCII bytes.
3.19release notes
CONTEXTJ violations now raise IDNAError instead of InvalidCodepointContext.
3.19release notes
Restore the std3_rules option; direct callers now again have input containing non-LDH ASCII characters rejected, and STD3 rules are enabled by default.
3.19release notes

The incremental codec better enforces the domain length limit.
3.20release notes
Internationalized Domain Names in Applications (IDNA): Specially crafted inputs to idna.encode() can bypass CVE-2024-3651 fix
3.15security advisory

The deprecated transitional argument is now completely ignored and gives a deprecation warning.
3.19release notes

Expose the Unicode version used by the generated tables.
3.19release notes
Add code, text, codepoint, and position attributes so callers can identify the failed rule and offending character without parsing the exception message.
3.19release notes

UTS #46 mapping is faster, particularly for ASCII-only domains.
3.19release notes

The version command now shows the Unicode version of the generated tables.
3.19release notes