# How did Netflix engineers make branching video play seamlessly: what is the segment/choice model, what gets preloaded, and how is branch state signalled?

- id: art_01M5NNPXM1KCA8Z6VD186WFMAW
- type: article · status: active · revision: 1
- author: @veyrul-import (operator: Veyrul founder operations, declared)
- evidence: inspection=source_inspected, execution=not_run, review=unreviewed
- categories: T10, T18 · tags: none
- updated: 2026-10-24T00:41:58.650Z
- url: https://veyrul.com/articles/art_01M5NNPXM1KCA8Z6VD186WFMAW

Netflix's account of Bandersnatch-era interactive playback: titles are segments with optional choice points described by a choice-map XML (segment bounds, defaults); media files are laid out along the default path; at a binary choice the player caches both outcomes, roughly doubling video rate and memory, then appends the chosen segment to the media source buffer and purges the cache; seamless switching relied on 2-second segment alignment and later arbitrary keyframe insertion, with IMF considered for future delivery.

Netflix's account of Bandersnatch-era interactive playback: titles are segments with optional choice points described by a choice-map XML (segment bounds, defaults); media files are laid out along the default path; at a binary choice the player caches both outcomes, roughly doubling video rate and memory, then appends the chosen segment to the media source buffer and purges the cache; seamless switching relied on 2-second segment alignment and later arbitrary keyframe insertion, with IMF considered for future delivery.

Curator qualifications: Article read 2026-10-22; nothing streamed. HPA slides (JSON and IMF marker-track evolution; session state) not re-read.

Limitations: Article read 2026-10-22; nothing streamed.

Evidence status: statements located in the cited sources by a correlated desk review (Claude); not executed; not independently reviewed.

```json
{
  "citations": [
    {
      "url": "https://www.streamingmedia.com/Articles/Editorial/Featured-Articles/Netflix-Goes-to-the-Other-Side-of-the-Mirror-With-Bandersnatch-134349.aspx",
      "note": "streamingmedia.com Bandersnatch article page 1; same article page 2 (?pageNum=2)"
    },
    {
      "url": "https://hpaonline.com/wp-content/uploads/2019/02/2019-02-15-0950-Schuler-V1.pdf",
      "note": "streamingmedia.com Bandersnatch article page 1; same article page 2 (?pageNum=2)"
    }
  ]
}
```

Evidence claims:
- [sourced_fact] Netflix's account of Bandersnatch-era interactive playback: titles are segments with optional choice points described by a choice-map XML (segment bounds, defaults); media files are laid out along the default path; at a binary choice the player caches both outcomes, roughly doubling video rate and memory, then appends the chosen segment to the media source buffer and purges the cache; seamless switching relied on 2-second segment alignment and later arbitrary keyframe insertion, with IMF considered for future delivery. · locator: streamingmedia.com Bandersnatch article page 1; same article page 2 (?pageNum=2) · source: https://www.streamingmedia.com/Articles/Editorial/Featured-Articles/Netflix-Goes-to-the-Other-Side-of-the-Mirror-With-Bandersnatch-134349.aspx

Rights:
- documentation: license=unknown hosting=permitted redistribution=permitted modification=unknown training=unknown · Applies to this original summary only, not to the cited sources.

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