Azure App Service not working, no module named uvicorn

Question

Azure App Service not working, no module named uvicorn

Shaelin Murphy 20

My Azure App Service API says that it is running, but I keep getting this error in the logs:
2026-03-25T16:49:12.1041839Z /opt/python/3.11.14/bin/python: No module named uvicorn
However, this module is in my requirements.txt and has been for some time. The app stopped working suddenly.

Why might this be happening? Since nothing else about the app has changed.

Praneeth Maddali 7,315 Reputation points Microsoft External Staff Moderator

2026-03-25T17:37:35.0666667+00:00
HI @Shaelin Murphy

Thanks for reaching us regarding your issue “/opt/python/3.11.14/bin/python: No module named uvicorn” error pop up quite a few times with FastAPI apps on Azure App Service Linux. Even though uvicorn has been in your requirements.txt for a while, the app suddenly stops because the Oryx build step (which installs your dependencies into the runtime environment) isn’t running.

The fix is usually just two quick config changes plus a redeploy:

To enable the build during deployment, navigate to your App Service in the Azure portal. Then, select Configuration, go to Application settings, and add the following:

Name: SCM_DO_BUILD_DURING_DEPLOYMENT

Value: true (Do this before you redeploy.)

In Configuration >General settings, please ensure that you update the Startup Command accordingly. Replace "main:app" with the appropriate file and application name as required.

Recommended (Gunicorn + Uvicorn worker): gunicorn -w 2 -k uvicorn.workers.UvicornWorker --bind=0.0.0.0:$PORT main:app

Or simple Uvicorn: python -m uvicorn main:app --host 0.0.0.0 --port $PORT

After saving, redeploy your code (zip deploy, Git push, or az webapp deploy). You should then see the pip install -r requirements.txt step in the log stream, and uvicorn will be available.

Reference:

https://learn.microsoft.com/en-us/azure/app-service/configure-language-python

https://learn.microsoft.com/en-us/azure/developer/python/configure-python-web-app-on-app-service

https://learn.microsoft.com/en-us/azure/app-service/quickstart-python?tabs=flask%2Cwindows%2Cazure-cli%2Cazure-cli-deploy%2Cdeploy-instructions-azportal%2Cterminal-bash%2Cdeploy-instructions-zip-azcli

Kindly let us know if the above helps or you need further assistance on this issue.

Please "upvote" if the information helped you. This will help us and others in the community as well.
Shaelin Murphy 20 Reputation points

2026-03-26T02:06:31.69+00:00

Hi! Thanks for your reply. I already had both of your two steps configured that way.
Is there anything else that could be causing this issue?
Shaelin Murphy 20 Reputation points

2026-03-27T16:11:46.4133333+00:00

I figured it out, thank you.
Praneeth Maddali 7,315 Reputation points Microsoft External Staff Moderator

2026-03-27T18:10:47.5666667+00:00

HI @Shaelin Murphy

I’m glad to hear your positive response and appreciate you sharing the update.

Just checking in to see if the earlier answer helped resolve your query. If it did, please click “Accept the answer” and consider upvoting it—this can be helpful for other community members who might face a similar issue.

If you have any further questions or need additional assistance, please feel free to let us know. We’re here to help!

1 answer

Your answer

Praneeth Maddali 7,315 Reputation points Microsoft External Staff Moderator

2026-03-25T17:37:35.0666667+00:00

HI @Shaelin Murphy

Thanks for reaching us regarding your issue “/opt/python/3.11.14/bin/python: No module named uvicorn” error pop up quite a few times with FastAPI apps on Azure App Service Linux. Even though uvicorn has been in your requirements.txt for a while, the app suddenly stops because the Oryx build step (which installs your dependencies into the runtime environment) isn’t running.

The fix is usually just two quick config changes plus a redeploy:

To enable the build during deployment, navigate to your App Service in the Azure portal. Then, select Configuration, go to Application settings, and add the following:

Name: SCM_DO_BUILD_DURING_DEPLOYMENT

Value: true (Do this before you redeploy.)

In Configuration >General settings, please ensure that you update the Startup Command accordingly. Replace "main:app" with the appropriate file and application name as required.

Recommended (Gunicorn + Uvicorn worker): gunicorn -w 2 -k uvicorn.workers.UvicornWorker --bind=0.0.0.0:$PORT main:app

Or simple Uvicorn: python -m uvicorn main:app --host 0.0.0.0 --port $PORT

After saving, redeploy your code (zip deploy, Git push, or az webapp deploy). You should then see the pip install -r requirements.txt step in the log stream, and uvicorn will be available.

Reference:

https://learn.microsoft.com/en-us/azure/app-service/configure-language-python

https://learn.microsoft.com/en-us/azure/developer/python/configure-python-web-app-on-app-service

https://learn.microsoft.com/en-us/azure/app-service/quickstart-python?tabs=flask%2Cwindows%2Cazure-cli%2Cazure-cli-deploy%2Cdeploy-instructions-azportal%2Cterminal-bash%2Cdeploy-instructions-zip-azcli

Kindly let us know if the above helps or you need further assistance on this issue.

Please "upvote" if the information helped you. This will help us and others in the community as well.
Shaelin Murphy 20 Reputation points

2026-03-26T02:06:31.69+00:00

Hi! Thanks for your reply. I already had both of your two steps configured that way.
Is there anything else that could be causing this issue?
Shaelin Murphy 20 Reputation points

2026-03-27T16:11:46.4133333+00:00

I figured it out, thank you.
Praneeth Maddali 7,315 Reputation points Microsoft External Staff Moderator

2026-03-27T18:10:47.5666667+00:00

HI @Shaelin Murphy

I’m glad to hear your positive response and appreciate you sharing the update.

Just checking in to see if the earlier answer helped resolve your query. If it did, please click “Accept the answer” and consider upvoting it—this can be helpful for other community members who might face a similar issue.

If you have any further questions or need additional assistance, please feel free to let us know. We’re here to help!

Answer 1

Praneeth Maddali 7,315 Microsoft External Staff Moderator

HI @Shaelin Murphy

Thank you for confirming—that really helps narrow things down.

Since SCM_DO_BUILD_DURING_DEPLOYMENT is already set to true and the startup command is configured, here are some other common reasons why you might still see the "No module named uvicorn" error:

The WEBSITE_RUN_FROM_PACKAGE conflict happens frequently. This setting is commonly used for zip deployments and can stop the Oryx build from running, even if SCM_DO_BUILD_DURING_DEPLOYMENT is enabled. To resolve this, check Configuration > Application settings for WEBSITE_RUN_FROM_PACKAGE. If it's set to 1, remove it or change it to 0, then save and redeploy your code.
Check that the Oryx build completed successfully. After redeploying, review the Log stream or Deployment logs for entries such as: Running pip install -r requirements.txt. If this step is missing or shows errors, the virtual environment (antenv) will not have uvicorn installed.
```
   Running pip install -r requirements.txt
```
Please ensure that your deployment package does not include any local virtual environment folders such as .venv, venv, or antenv. Oryx will handle the creation and management of its own virtual environment.
Please ensure that the requirements.txt file is located at the root of your deployed package and that it includes uvicorn—preferably uvicorn[standard], or uvicorn together with gunicorn.

reference:

https://azureossd.github.io/2022/11/24/Python-on-Linux-App-Service-and-ModuleNotFound-Errors/

https://learn.microsoft.com/en-us/azure/app-service/configure-language-python

https://learn.microsoft.com/en-us/azure/app-service/quickstart-python?tabs=flask%2Cwindows%2Cazure-cli%2Cazure-cli-deploy%2Cdeploy-instructions-azportal%2Cterminal-bash%2Cdeploy-instructions-zip-azcli

If the answer is helpful, Please do click "Accept the answer” and Yes, this can be beneficial to other community members.

If you have any other questions, let me know in the "comments" and I would be happy to help you

Shaelin Murphy 20 Reputation points

2026-04-02T13:03:25.51+00:00

No, this answer did not work.

I have a FastAPI app deployed on Azure App Service (Linux), and I keep running into a frustrating issue that seems random.

Most of the time, my app deploys and runs correctly. The startup command and requirements.txt are set properly, and everything works. But after a few redeploys, the app will suddenly fail to start and begin showing errors like:

WARNING: Could not find virtual environment directory /home/site/wwwroot/antenv WARNING: Could not find package directory /home/site/wwwroot/oryx_packages. /opt/python/3.11.14/bin/python: No module named uvicorn

Could not find build manifest file at '/home/site/wwwroot/oryx-manifest.toml'

What is confusing is that nothing meaningful has changed in my startup command or dependencies. A deployment can work fine several times in a row, and then a later redeploy will suddenly fail with these missing environment/package errors.

Is there a reliable way to force App Service to always rebuild/install dependencies on each deploy?
Praneeth Maddali 7,315 Reputation points Microsoft External Staff Moderator

2026-04-02T16:23:14.36+00:00
HI @Shaelin Murphy

Thanks for sharing those specific log warnings — this is very helpful. The errors you’re seeing (Could not find virtual environment directory /home/site/wwwroot/antenv, oryx_packages, and oryx-manifest.toml) point to a known intermittent Oryx build cache issue on Azure App Service Linux. The build artifacts sometimes become stale or incomplete after multiple redeploys, even when nothing in your code or configuration has changed. This is why the app works fine several times and then suddenly fails with “No module named uvicorn”.

Quick Fix – Force a Clean Rebuild

When this happens again, do the following:

Go to your App Service > Advanced Tools (Kudu) >Debug console > Bash

Run these commands:
rm -rf /home/site/wwwroot/antenv rm -rf /home/site/wwwroot/__oryx_packages__ rm -f /home/site/wwwroot/oryx-manifest.toml

Make sure these two settings are configured correctly:

SCM_DO_BUILD_DURING_DEPLOYMENT = true

WEBSITE_RUN_FROM_PACKAGE = 0 (or completely remove this setting)

Redeploy the app and check the log stream for the line: Running pip install -r requirements.txt

This combination forces Oryx to create a fresh virtual environment.

Long-term Recommendation

If this intermittent behavior continues to frustrate you, the most reliable solution is to deploy your FastAPI app as a custom Docker container. This completely bypasses Oryx and guarantees consistent dependencies on every deploy. Microsoft recommends this approach for production workloads that need predictability.

Reference :

https://azureossd.github.io/2022/11/24/Python-on-Linux-App-Service-and-ModuleNotFound-Errors/

https://learn.microsoft.com/en-us/azure/app-service/configure-language-python

https://learn.microsoft.com/en-us/azure/app-service/quickstart-python?tabs=flask%2Cwindows%2Cazure-cli%2Cazure-cli-deploy%2Cdeploy-instructions-azportal%2Cterminal-bash%2Cdeploy-instructions-zip-azcli

Kindly let us know if the above helps or you need further assistance on this issue.

Please "upvote" if the information helped you. This will help us and others in the community as well.
Praneeth Maddali 7,315 Reputation points Microsoft External Staff Moderator

2026-04-03T19:10:27.1033333+00:00

HI @Shaelin Murphy

Just following up to see if your issue has been resolved or if you had a chance to review my earlier comment?

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Azure App Service not working, no module named uvicorn

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