Use WebVTT cue identifiers for stable editorial comparisons

The useful distinctions

• WebVTT cues can carry identifiers before their timing lines.
• An identifier is exposed through TextTrackCue.id.
• The current WebVTT authoring syntax requires cue identifiers to be unique within a file.

Choose an identity that survives a timing edit

The sample names two fictional steps by editorial identity rather than using their start time as a key. If the second step shifts by half a second in a later edit, it can retain the identifier fold-outer. A comparison tool can then report one changed timing interval instead of treating the old cue as deleted and the new one as unrelated. The naming policy is an original workflow convention; the format does not require these particular words or a timestamp-free naming scheme.

Audit identifiers before relying on them

Identifiers are strings, so preserve spelling exactly when joining revisions. A duplicate can make an editorial lookup ambiguous even if a permissive parser still produces visible cues. Check uniqueness before using identifiers as database keys and keep track identity as a separate part of the key when comparing multiple language files. An identifier is not payload text and should not be inserted into translated dialogue. It also does not establish that two cues in different tracks convey equivalent meaning. For a split or merged cue, record the editorial relationship explicitly rather than reusing one identifier for several new blocks and hoping file order will resolve the ambiguity.

Worked example · synthetic

The two identifiers are distinct and occur on their own lines before timings. A later timestamp correction can retain fold-outer while changing its interval; this is a suggested editorial policy, not a playback guarantee.

Synthetic text example; no network operation has been performed.

WEBVTT

fold-inner
00:00:02.000 --> 00:00:04.000
Fold the inner corner.

fold-outer
00:00:04.500 --> 00:00:06.500
Fold the outer corner.

Check the interpretation

• Reject duplicate identifiers in an authoring check.
• Use track identity plus cue id for cross-file comparisons.
• Keep IDs distinct from displayed payload text.