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Local-first software and CRDTs (BOB 2025 keynote)

Summary

This keynote by Annette Bieniusa at BOB Konferenz 2025 explains local-first software. In this approach, apps keep and process data mainly on the user's devices instead of a central server. That lets them work offline, respond faster and give users control of their data. Sync between devices relies on techniques such as CRDTs (Conflict-free Replicated Data Types), which merge offline edits automatically.

Draft. License: CC BY 4.0 (this summary). Sources: [S1] media.ccc.de / BOB Konferenz, "Keynote: Local-first Software (BOB Konferenz 2025)" (CC BY 3.0 DE).

Talk

• Speaker: Annette Bieniusa
• Event: BOB Konferenz 2025 (2025-03-14)
• Video: https://media.ccc.de/v/bob11-2025-local-first-software-bieniusa
• License: CC BY 3.0 DE (stated on the media.ccc.de page, checked 2026-11-02)

Related

• fosdem-2025-privacy-first-architecture (published)

Facts

• id: F1 claim: Local-first applications store and process data primarily on users' devices rather than depending on continuous connectivity to a central server. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F2 claim: Claimed benefits: usable without internet, faster interactions without server round-trips, and more user control over data. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F3 claim: Local-first architectures usually include synchronization for collaboration and sharing across devices. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F4 claim: CRDTs (Conflict-free Replicated Data Types) let updates made on different devices, even offline, be reconciled automatically. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02
• id: F5 claim: The talk covers CRDT internals, implementation strategies, developer challenges, case studies such as collaborative spreadsheets, and methods for verifying correctness of local-first apps. confidence: medium date: 2026-11-02 sources: [S1] license: CC BY 4.0 checked_on: 2026-11-02

Caveats

• Summarized from the official talk description on media.ccc.de; the video itself was not transcribed for this draft.
• CRDTs guarantee convergence, not that the merged result matches what users intended.

Pointers

• id: P1 answers: Full talk video where: https://media.ccc.de/v/bob11-2025-local-first-software-bieniusa access: free, public web page

@misc{iil_note_qs35dk7v,
  author = {{iinventedlight Library}},
  title = {{Local-first software and CRDTs (BOB 2025 keynote)}},
  howpublished = {iinventedlight Library},
  year = {2026},
  date = {2026-11-02},
  url = {https://iinventedlight.com/library/reference/talks/bob-2025-local-first-software/},
  note = {Permanent ID iil:note:qs35dk7v. License: CC-BY-4.0. Summary of https://media.ccc.de/v/bob11-2025-local-first-software-bieniusa.},
}

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