vs

Faiss vs hnswlib

Faiss: Meta's C++/Python library for fast dense-vector similarity search and clustering, CPU and GPU. hnswlib: Header-only C++ HNSW library with Python bindings, from the authors of the HNSW algorithm.

key differences

  • Faiss is built for larger datasets (≤ 1 PB) than hnswlib (≤ 10 TB).
  • Only Faiss has compression.

choose faiss for

  • +Embedding similarity search inside ML pipelines
  • +Offline deduplication and clustering
  • +Building custom vector search services
  • +ANN research and benchmarking

best at · Vector search, Embedded, Scientific

choose hnswlib for

  • +Embedding HNSW in applications
  • +Baseline for ANN benchmarks
  • +Small in-process semantic search

best at · Vector search, Embedded

overview
Primary model
Vector
Vector
Also supports
–
–
Type
Embedded library
Embedded library
Status
Active
Active
Developer
Meta (FAIR)
nmslib contributors
First release
2017
2017
Latest version
1.15.1 (Sep 16, 2026)
0.9.0 (Mar 28, 2026)
License
Open source (permissive)MIT License
Open source (permissive)Apache License 2.0
Free tier
✓
✓
popularity
WhichDB Score
44.7
15.5
Rank
#40
#211
GitHub stars
41.2K
5.4K
Stack Overflow questions
134
–
scale & guarantees
Comfortable data size
Large (≤ 1 PB)
Medium (≤ 10 TB)
Horizontal scaling
Manual
Manual
Multi-region
None
None
ACID
None
None
Consistency
Strong
Strong
Schema
Schemaless
Schemaless
Architecture
Embedded, In memory
Embedded, In memory
deployment
Self-hosted
✓
✓
Vendor-managed cloud
—
—
Serverless
—
—
Embedded
✓
✓
Edge
—
—
Clouds
–
–
capabilities
Transactions
—
—
Joins
—
—
Secondary indexes
—
—
Full-text search
—
—
Vector search
✓
✓
Geospatial
—
—
JSON
—
—
Change data capture
—
—
Triggers
—
—
Stored procedures
—
—
Materialized views
—
—
TTL / expiry
—
—
Pub/Sub
—
—
Columnar storage
—
—
In-memory
✓
✓
Durable persistence
—
—
Compression
✓
—
Encryption at rest
—
—
Role-based access
—
—
Time travel
—
—
Branching
—
—
Online schema changes
—
—
Streaming ingest
—
—
Offline sync
—
—
Runs in WebAssembly
—
—
interfaces
Query languages
C++ API, Python API
Library API
Client languages
C++, Python, C
C++, Python
Best for
Vector search, Embedded, Scientific
Vector search, Embedded

Faiss vs hnswlib: FAQ

What is the difference between Faiss and hnswlib?

Faiss: Meta's C++/Python library for fast dense-vector similarity search and clustering, CPU and GPU. hnswlib: Header-only C++ HNSW library with Python bindings, from the authors of the HNSW algorithm. Faiss is built for larger datasets (≤ 1 PB) than hnswlib (≤ 10 TB). Only Faiss has compression.

When should I choose Faiss over hnswlib?

Choose Faiss for embedding similarity search inside ML pipelines; offline deduplication and clustering; and building custom vector search services. Choose hnswlib for embedding HNSW in applications, baseline for ANN benchmarks and small in-process semantic search.

Is Faiss or hnswlib more popular?

Faiss ranks #40 on the WhichDB Score (44.7/100) and hnswlib ranks #211 (15.5/100). Popularity is not fit: check the requirements that matter for your project.

Are Faiss and hnswlib open source?

Yes. Faiss is open source. License: MIT License. Yes. hnswlib is open source. License: Apache License 2.0.