See the shape of your data. Dataspex is a point-and-click Clojure(Script) data browser that lets you peer into maps, vectors, and seqs; explore Datascript and Datomic connections; trace changes to atoms and databases over time; and more -- with minimal effort and a short learning curve.

no.cjohansen/dataspex {:mvn/version "2025.05.7"}

Dataspex runs as a Chrome and Firefox extension — or as a standalone web app — and connects to local ClojureScript apps, Clojure REPLs, or across the network so you can debug apps on your phone.

Whether you're debugging a live system or scrying the hidden structure of your app state, Dataspex gives you eyes on the flow.

Dataspex is the spiritual successor to Gadget Inspector.

Using Dataspex is easy: require dataspex.core and call inspect on your data. When used from Clojure, it will start a server on port 7117. The browser extension automatically connects to this port.

(require '[dataspex.core :as dataspex])

;; Atoms will automatically be watched for changes, including a live updated
;; changelog with diffs
(def store (atom {}))
(dataspex/inspect "App state" store)

;; Inspect any piece of data with a label. Multiple calls to `inspect` with the
;; same label will update Dataspex' view of the data, and produce an audit
;; trail.
(def page-data {:title "My page"})
(dataspex/inspect "Page data" page-data)

;; Datascript databases can be viewed through a custom UI
(require '[datascript.core :as d])
(def conn
  (d/create-conn
   {:person/id {:db/unique :db.unique/identity}
    :person/friends {:db/valueType :db.type/ref
                     :db/cardinality :db.cardinality/many}}))

,,,

(dataspex/inspect "DB" conn)

;; Inspect taps
(dataspex/inspect-taps)

Display data from your ClojureScript app and/or JVM backend live in your browser's devtools panel, and enjoy a bunch of finely tuned point-and-click features, including:

• Browse immutable data
• Browse JavaScript objects, arrays and dates
• Browse JWT strings
• Browse any data that implements clojure.core.protocols/Datafiable
• Browse Datascript databases, indexes and entities
• Browse Datomic databases and entities (indexes to follow)
• Navigate Datascript/Datomic refs, including reverse refs
• Browse sequences of maps in tables
• Browse meta data of data
• View full data in "syntax highlight mode"
• Browse hiccup with customized rendering
• Copy data at any point in the datastructure
• Paginate large or indefinite data structures
• Consistently sort collections (including respecting indexed and sorted ones)
• View changes to inspected data over time, including diffs
• Browse any historic version of inspected data, side-by-side with other versions
• Light and dark themes
• Build custom views for your own data types by implementing the various rendering protocols.

And much more.

To build the Chrome extension:

make chrome-extension

Then go to chrome://extensions/, enable devtools, and click "Load unpacked". Choose the brower-extension directory in this repo, and you should be good to go.

To build the Firefox extension:

make firefox-extension

You will need Firefox Developer Edition.

1. Go to about:config
2. Set devtools.chrome.enabled to true
3. Set devtools.debugger.remote-enabled to true
4. Set devtools.debugger.prompt-connection to false (optional, reduces prompts)
5. Set extensions.webextensions.remote to true (required for devtools extensions)
6. Go to about:debugging
7. Click "This Firefox" in the sidebar
8. Click "Load Temporary Add-on"
9. Select manifest.json from the browser-extension/firefox folder

If you make changes to the extension code, click "reload".

Copyright © 2025 Christian Johansen. Distributed under the MIT License.