Skip to main content
This is a pre-production deployment of Warehouse. Changes made here affect the production instance of PyPI (
Help us improve Python packaging - Donate today!

Web interface for Python's built-in PDB debugger

Project Description


Web-PDB is a web-interface for Python’s built-in PDB debugger. It allows to debug Python scripts remotely in a web-browser.


  • Responsive design based on Bootstrap.
  • Python syntax highlighting with Prism (“Okaida” theme).
  • Supports all PDB features.
  • Standard input and output can be redirected to the web-console to interact with Python scripts remotely.
  • Current file box tracks current position in a file being executed. Red line numbers indicate breakpoints, if any.
  • Globals and Locals boxes show local and global variables in the current scope. Special variables that start and end with double underscores __ are excluded (you can always view them using PDB commands).
  • Human-readable Unicode literals for Python 2.
  • Command history that stores up to 10 last unique PDB commands (accessed by arrow UP/DOWN keys).

Web-PDB console in Chrome browser


Install Web-PDB into your working Python environment:

pip install web-pdb

Insert the following line into your Python program at the point where you want to start debugging:

import web_pdb; web_pdb.set_trace()

The set_trace() call will suspend your program and open a web-UI at the default port 5555 (port value can be changed). Enter in your browser’s address bar: http://<your Python machine hostname or IP>:5555, for example http://monty-python:5555, and you should see the web-UI like the one on the preceding screenshot. Now you can use all PDB commands and features. Additional Current file, Globals and Locals information boxes help you better track your program runtime state.

Note: it is strongly recommended to work with the Web-PDB web-UI only in one browser session. With more than one browser window accessing the web-UI it can display incorrect data in one or more browser sessions.

Subsequent set_trace() calls can be used as hardcoded breakpoints.

Additionally, Web-PDB provides catch_post_mortem context manager that can catch unhandled exceptions raised within its scope and automatically start PDB post-mortem debugging session. For example:

import web_pdb

with web_pdb.catch_post_mortem():
    # Some error-prone code
    assert foo == bar, 'Oops!'

For more detailed info about the Web-PDB API read docstrings in the ./web_pdb/ file.

Note: Web-PDB periodically sends AJAX GET requests to /output/update endpoint. This is normal behaviour.

Considerations for Multithreading and Multiprocessing Programs


Web-PDB maintains one debugger instance that traces only one thread. You should not call set_trace() from different threads to avoid race conditions. Each thread needs to be debugged separately one at a time.


Each process can have its own debugger instance provided you call set_trace with a different port value for each process. This way you can debug each process in a separate browser tab/window. To simplify this you can use set_trace(port=-1) to select a random port between 32768 and 65536.


  • Python: 2.7, 3+
  • Browsers: Firefox, Chrome (all modern browsers should work)


MIT, see LICENSE.txt.

The debugger icon made by Freepik from is licensed by CC 3.0 BY.



  • Fix a bug with patched cl command not working.


  • Fixed setting set_trace() at the last line of a Python script.
  • Fixed clearing a breakpoint at setups with the current workdir different from the current module directory.


  • Internal changes.


  • Now if web-console data haven’t changed the back-end sends “null” response body instead of a 403 error.


  • Implemented a multi-threaded WSGI server to increase responsiveness of the web-UI.


  • Added deflate compression for data sent to a browser.
  • Attempt to fix Current file box auto-scrolling.


  • Logger fix.


  • Minor UI redesign.
  • Added a quick action toolbar and hotkeys for common commands.
  • Added a quick help dialog.
  • Breakpoints can be added/deleted with a click on a line number.
  • The Currrent file box is not auto-scrolled if the current line hasn’t changed.
  • Multiple set_trace() and post_mortem() calls are processed correctly.
  • Added random web-UI port selection with port=-1.


  • Initial PyPI release

Release History

This version
History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


History Node


Download Files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Filename, Size & Hash SHA256 Hash Help File Type Python Version Upload Date
(202.6 kB) Copy SHA256 Hash SHA256
Wheel py2.py3 Jan 4, 2018
(198.1 kB) Copy SHA256 Hash SHA256
Source None Jan 4, 2018

Supported By

Elastic Elastic Search Pingdom Pingdom Monitoring Dyn Dyn DNS Sentry Sentry Error Logging CloudAMQP CloudAMQP RabbitMQ Heroku Heroku PaaS Kabu Creative Kabu Creative UX & Design Fastly Fastly CDN DigiCert DigiCert EV Certificate Google Google Cloud Servers DreamHost DreamHost Log Hosting