Codex
Connectome Data Explorer
Developed at Princeton Neuroscience Institute
Sign in to browse brain maps
Explore and analyze large-scale connectomes without installing software or downloading massive datasets.
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Why is sign-in required?
Codex is used by a wide audience, from scientists to high school programs, and as of early 2026, over 60,000 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 v0.9 (CNS)
Male Adult Fly Brain and Nerve Cord
166,694 neurons
6,239,112 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
