Codespaces opens then fails saying "Oh no, it looks like you're offline!"

[jmusone]

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Frankly I just don't know how to resolve this issue. My codespace is called symmetrical-engine-g7r74prxvx6c96wg and the first failing API call is POST https://symmetrical-engine-g7r74prxvx6c96wg.github.dev/diagnostic?cors=true&content-type=application/x-json-stream&w=0

I've attached the console logs. I also checked the troubleshooting guide and none of it seemed to apply to me, but maybe I'm misinterpreting. Would appreciate any help!

console-export-2025-8-19_21-37-56.log

[amer-5]

Hi jmusone,

The “Oh no, it looks like you’re offline!” message usually means the browser or Codespace client can’t reach the Codespaces backend. A few things to check:

1. Network connectivity – Ensure your internet connection is stable and no firewall or VPN is blocking *.github.dev or Codespaces endpoints.
2. Browser caching – Try clearing cache or opening Codespaces in an incognito/private window.
3. Browser compatibility – Make sure you’re using a supported browser (Chrome, Edge, or Firefox latest versions).
4. Sign-in session – Log out of GitHub and log back in, sometimes stale tokens cause API failures.
5. Restart Codespace – From GitHub → Codespaces, stop and start the Codespace again.

If these steps don’t help, the attached console logs can be shared with GitHub support—they can inspect backend errors for your specific Codespace.

[jmusone]

Hey, thanks for the feedback! Tried all of these and still running into the same issue, so how do I get in touch with support? I thought this was it to be honest

[amer-5]

Hi again,

If you’ve already gone through those steps and the issue persists, the best way to reach GitHub Support is:

Go to GitHub Support portal
and open a new ticket.

Choose Codespaces as the product area, and include the failing Codespace name (symmetrical-engine-g7r74prxvx6c96wg) along with your console logs.

If you’re on a paid plan (Pro, Team, Enterprise), you’ll have direct support access. If you’re on free, you can still report the problem via the contact form and GitHub staff will review it.

Since you’ve already collected the console logs, attaching them in the ticket will really speed up investigation.

Hope that helps!

[xvvvyz]

For anyone using Firefox that comes across this issue:

Changing Settings > Privacy & Security > Enhanced Tracking Protection from Strict to Standard fixed it for me.

[bradley-varol]

Thanks!

[AbdulAhadQSol]

Try another browser or open Codespaces in private/incognito mode.

Disable or adjust privacy/tracking protections (in Firefox or any browser) to see if that changes things.

Check logs/console for any specific error messages (like certain resources failing to load, certificate errors, CORS errors, etc.).

Check whether your network or firewall might be blocking *.github.dev or the Codespaces backend domains. If possible try a different network.

Stop / restart the codespace via GitHub → Codespaces dashboard.

Clear cookies / log out of GitHub, then log in fresh.

Check the GitHub status page to see if Codespaces services are experiencing outages.

If none of these resolve it, collect console logs and any error response codes, then open a ticket with GitHub Support, including the codespace name (“symmetrical-engine-g7r74prxvx6c96wg”) and the logs.

[eggduzao]

Hi there - thanks for sharing the details and the console logs, that helps.

---

tl;dr

In short: the github.dev endpoint isn't a static service - it's just a routing layer to your live Codespace. If the Codespace isn't running, those endpoints will fail no matter what the code is doing. Starting the Codespace and checking port forwarding usually resolves this.

---

From what I can see, the error isn't coming from your code directly but rather from the Codespaces instance URL itself. When you spin up a Codespace, GitHub gives it a temporary subdomain like:

https://<codespace-name>.github.dev/

That URL only works while the Codespace is actively running. If the Codespace is stopped, suspended, or has timed out, any API call to it will return network/unauthorized style errors (since the backend container is literally offline).

A few things you can try:

1. Check that your Codespace is running

   • Go to github.com/codespaces
   • Find the symmetrical-engine-g7r74prxvx6c96wg instance
   • Make sure it shows as "Running". If not, start it again.

2. Reconnect to the Codespace

   • Sometimes the browser loses connection if the Codespace restarted.
   • Refresh the github.dev tab or re-open the Codespace from GitHub.

3. Confirm port forwarding (if applicable)

   • If your project exposes an API, you'll want to check that the port is forwarded in the Codespaces ports panel.
   • When a port is forwarded, Codespaces gives you a public URL you can use for API calls. Without forwarding, only the Codespace itself can talk to that service.

4. Re-run your diagnostic call

   • Once the Codespace is confirmed running, try the POST again.
   • If it succeeds, then the root cause was simply that the container had gone offline.