Codex
Connectome Data Explorer
FlyWire Codex is a free platform for exploring detailed fly connectomes, searching neurons, and analyzing synaptic connections.
Developed at Princeton Neuroscience InstituteSign in to browse brain maps
Explore and analyze large-scale connectomes without installing software or downloading massive datasets.
FlyWire and Codex are hosted by the
Princeton Neuroscience Institute
of Princeton University.
By signing in, you agree to the
FlyWire Terms of Service & Privacy Notice.
Why is sign-in required?
Codex is used by a wide audience, from scientists to high school programs, and as of 2026, over 100,000 users have signed in. To keep Codex free, fast, and available to everyone, access to its apps requires signing in with a Google account. This helps prevent abuse, enables rate-limiting of excessive usage, and reduces server load from automated or malicious activity.
Some static pages can be viewed without logging in, but any feature that performs computations on our servers requires you to be signed in. If you don’t have a Google account and can’t create one, please contact flywire@princeton.edu.
For general information, visit the FlyWire homepage.
What's a connectome?
A connectome is a wiring diagram of a brain or nervous system - a map of its neurons and the synaptic connections between them.
For the first time, we can explore an adult fruit fly’s entire brain neuron by neuron: about 150K neurons connected by more than 50M synapses.
It is the most complete brain-wide connectome yet produced for an adult animal capable of complex behavior. Fruit flies navigate a three-dimensional world, learn, form memories, court and fight - all with a brain smaller than a grain of sand.
datasets
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FAFB v783 (CB)
Female Adult Fly Brain
139,255 neurons
3,732,460 connections -
BANC v888 (CNS)
Female Adult Fly Brain and Nerve Cord
158,262 neurons
3,037,361 connections -
MANC v1.2.1 (VNC)
Male Adult Fly Nerve Cord
23,665 neurons
5,305,638 connections -
MAOL v1.1 (OL/R)
Male Adult Fly Right Optic Lobe
52,445 neurons
6,484,936 connections -
MCNS v1.0 (CNS)
Male Adult Fly Brain and Nerve Cord
166,700 neurons
6,242,118 connections
apps
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Search
Find neurons using free-form or structured queries
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Stats
See statistics and charts for various attributes of all or subset of neurons in the dataset
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Annotations
Browse cell types, labels, and groupings of the neurons in the dataset
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Cell Details
Information about individual cells, their connectivity, similar/twin cells, 3D rendering and annotations
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Neuropils
Visualize and query connections in specific brain regions
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3D Viewer
Visualize queried neurons and synapses in annotated Neuroglancer scenes
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Network Graphs
Visualize connectivity of neurons and their synaptic links
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Pathways
Analyze shortest paths between pairs of neurons
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Download Data
Export raw data for analysis with other tools / programs
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Exodiac
Ask questions about connectomics and get help writing Codex queries.
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Cell Types
Browse cell types and compare their counts across datasets.
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Visual Cell Types Catalog
Explore visual neuron types in the optic lobe.
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Sample Queries
Start with examples for finding neurons, connections, and pathways.
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FlyWire Academy
Learn connectomics through guided lessons and interactive activities.
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Codex on GitHub
Explore the code, contribute, or run Codex locally.
news
- 100,000+
- unique user sign-ins
- 200+
- university affiliations
- 5,000,000+
- queries served
- <150 ms
- mean response time
- 99.99%
- availability
Exploring connectomes with Codex
- Princeton
- Harvard
- MIT
- Stanford
- Oxford
- Cambridge
- Yale
- Caltech
- ETH Zurich
- Imperial College London
- UC Berkeley
- Columbia
- Cornell
- UCLA
- Tsinghua University
- Peking University
- National University of Singapore
- University of Tokyo
- University of Michigan
- Brown
- EPFL
- University of Toronto
- NYU
- University of Washington
- UC San Diego
- Seoul National University
- UC Santa Barbara
- Georgetown University
- Hebrew University of Jerusalem
- Trinity College Dublin
- Tel Aviv University
- Boston University
- Brandeis University
- National Tsing Hua University
- Rutgers University
- Leipzig University
- University of Warsaw
- Hanyang University
- University of Würzburg
- UC Santa Cruz
- University of Puerto Rico
- (and many more)
Based on a usage analytics export covering Mar. 2023 to Sep. 2026: 5,950,230 recorded requests and 103,172 distinct email addresses. Sign-ins are counted by distinct email address, not individual login events. At least 297 universities were identified by email domain. Listed universities were selected by combined usage and do not imply institutional endorsement. Availability and response times are measured by a monitoring service that queries Codex from six continents every five minutes.
