diff --git a/DEVELOPER.md b/DEVELOPER.md
index 52642d7c7e556bba454350f92f9c4ce47e9e2902..5ec5309192a66e9292beed298a6b798499153c88 100644
--- a/DEVELOPER.md
+++ b/DEVELOPER.md
@@ -8,12 +8,12 @@ This Jupyter extension contains of two components:
 
 * written in Python
 * see [jupyter-openbis-extension/](jupyter-openbis-extension)
-* is registered with the `jupyter serverextension enable --py jupyter-openbis-extension` command
+* serverextension is registered with the `jupyter serverextension enable --py jupyter-openbis-extension` command
 * registration should happen automatically when installilng via `pip install jupyter-openbis-extension`
 * this serverextension is loaded whenever a Jupyter server is started – either `jupyter notebook` or `jupyter lab`
 * serverextension talks to openBIS instances via the [pyBIS module](https://pypi.org/project/PyBIS/)
 * serverextension also talks to the notebook extension (see below) via https
-* serverextension uses an instance of the [tornado webserver](https://www.tornadoweb.org/en/stable/) that is used by Jupyter
+* serverextension uses an instance of the [tornado webserver](https://www.tornadoweb.org/en/stable/) that is used by Jupyter server
 * downloads and uploads dataSets and openBIS metadata
 
 **Jupyter notebook extension** (aka Jupyter nbextension)
@@ -27,8 +27,29 @@ This Jupyter extension contains of two components:
 * displays the three prominent buttons (configuration, download, upload) inside a Jupyter notebook
 * talks to the Jupyter serverextension (see above) via https requests
 
+## Jupyter serverextension
 
+sources see [jupyter-openbis-extension/](jupyter-openbis-extension)
 
+[server.py](jupyter-openbis-extension/server.py) dispatches all requests coming from the nbextension. Currently, following endpoints are present:
 
- 
-   
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+* GET `/openbis/dataset/(?P<connection_name>.*)?/(?P<permId>.*)?/(?P<downloadPath>.*)` – downloads the files of a dataSet to the disk.
+* POST `/openbis/dataset/(?P<connection_name>.*)` – upload of dataSets
+* GET `/openbis/datasetTypes/(?P<connection_name>.*)` – receive a list of available dataSet types (including all properties)
+* GET `/openbis/sample/(?P<connection_name>.*)?/(?P<identifier>.*)` – receive a list of dataSets for a given sample or experiment identifier (should be *dataSets*, not *sample*)
+* GET/POST `/openbis/conns` – receive openBIS connections or create new ones
+* PUT `/openbis/conn/(?P<connection_name>.*)` – modifiy an existing openBIS connection
+
+[connection.py](jupyter-openbis-extension/connection.py) – handles the openBIS connections
+[dataset.py](jupyter-openbis-extension/dataset.py) – handles the dataSets (down- and upload)
+[sample.py](jupyter-openbis-extension/server.py) – returns the list of available dataSets
+
+
+## Jupyter nbextension
+
+[main.js](jupyter-openbis-extension/static/main.js) – Main entry point for the nbextension. Registers the connectionDialog, downloadDialog, and uploadDialog
+[connectionDialog.js](jupyter-openbis-extension/static/connectionDialog.js) – shows the connection dialog
+[downloadDialog.js](jupyter-openbis-extension/static/downloadDialog.js) – shows the download dialog
+[uploadDialog.js](jupyter-openbis-extension/static/uploadDialog.js) – shows the upload dialog
+[state.js](jupyter-openbis-extension/static/state.js) – stores some state information, e.g. current connection, last downloaded dataSet, last entered metadata etc.
+[common.js](jupyter-openbis-extension/static/common.js) – commonly used utilities, e.g. create feedback, create error message, get cookie
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