CueNorm Public Validator

Apple

Apple HLS Subtitles (WebVTT)

WebVTT subtitle files for Apple HTTP Live Streaming, with the mandatory X-TIMESTAMP-MAP header

Validate a file with this profile apple-hls-subtitle@1.0

Format: webvtt
Destination: Apple hls
Language: any
Specification: verified
Interoperability: unverified
Last checked: 2026-09-23

Validation rules

No rules of its own: only the checks below apply.

Always checked

Whatever the profile's rules: how the file is read (file reading, FILE_FORMAT_MISMATCH, NO_SUBTITLES_READ), the timing of a delivery (NON_POSITIVE_DURATION, SUBTITLES_OUT_OF_ORDER, SUBTITLE_OVERLAP) and the language of the subtitles (SOURCE_LANGUAGE_MISMATCH).

Sources

Apple

official

HTTP Live Streaming (HLS) authoring specification for Apple devices, §5 Subtitle requirements

Retrieved 2026-09-23 Open source document
IETF

official

RFC 8216 HTTP Live Streaming, §3.5 WebVTT

Open source document

This is a CueNorm profile based on published specifications. It is not endorsed by Apple.

Resolved profile hash, recorded in every report and deliverable:

5c272c581649a5086090bb5f2c592c013e78d95c31df3ca3481ace0f8103d019