---
title: "Local-first software and CRDTs (BOB 2025 keynote)"
license: CC-BY-4.0
license_url: https://creativecommons.org/licenses/by/4.0/
source: https://media.ccc.de/v/bob11-2025-local-first-software-bieniusa
source_license: "CC BY 3.0 DE"
attribution: "Summary by iinventedlight (AI-assisted). Source: media.ccc.de / BOB Konferenz, \"Keynote: Local-first Software (BOB Konferenz 2025)\" (CC BY 3.0 DE)."
condensed_by: "iinventedlight (Grok Bot, AI-assisted)"
fact_checked: 2026-11-02
date: 2026-11-02
status: reviewed
reviewed_on: 2026-11-02
category: talks
checked_on: 2026-11-02
license_url: https://creativecommons.org/licenses/by/4.0/
source: https://media.ccc.de/v/bob11-2025-local-first-software-bieniusa
source_license: "CC BY 3.0 DE (talk); summary in our own words"
attribution: "Summary by iinventedlight (AI-assisted), condensed and paraphrased; sources: Annette Bieniusa, \"Keynote: Local-first Software\", BOB Konferenz 2025, media.ccc.de (CC BY 3.0 DE)"
condensed_by: "iinventedlight (Grok Bot, AI-assisted)"
fact_checked: 2026-11-02
date: 2026-11-02
category: talks
tags: talks, local-first, crdt, distributed-systems, offline
checked_on: 2026-11-02
sources:
  - id: S1
    title: "Keynote: Local-first Software (BOB Konferenz 2025)"
    authors: "Annette Bieniusa"
    publisher: "media.ccc.de / BOB Konferenz"
    url: https://media.ccc.de/v/bob11-2025-local-first-software-bieniusa
    accessed: 2026-11-02
    license: "CC BY 3.0 DE"
    attribution: "Annette Bieniusa, \"Keynote: Local-first Software\", BOB Konferenz 2025, media.ccc.de (CC BY 3.0 DE)"
---
# Local-first software and CRDTs (BOB 2025 keynote)

# 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