Heroku Application Error Page
Quick answer
The generic 'Application error' page just means Heroku could not get a response from your app. The error code in heroku logs --tail (H10, H12, H14, R10...) tells you which problem it is.
Most likely fix: Read the logs first
How to fix it
Try these in order — the most common fix is first.
1. Read the logs first
- Run heroku logs --tail -a <app>
- Find the first at=error line and note the code (H10, H12, H14...)
- Use the matching guide for that code
Did this fix it?2. Check dynos are running
- Run heroku ps
- If there is no web dyno, run heroku ps:scale web=1
- Check you are not out of Eco dyno hours (H82)
Did this fix it?3. Restart the dynos
- Run heroku restart -a <app>
- Then watch heroku logs --tail while loading the page
Did this fix it?4. Check config vars and add-ons
- Run heroku config
- Confirm DATABASE_URL and secrets exist; heroku addons shows attached add-ons
Did this fix it?5. Roll back
- heroku releases then heroku rollback v<N> if it started after a deploy
Did this fix it?6. Check Heroku status
- H99 and platform incidents need no change on your side; check the Heroku status page and retry
Did this fix it?
Symptoms
Browser shows 'Application error - An error occurred in the application and your page could not be served'.
Why it happens
- App crashed (H10)
- No web dyno running (H14)
- Request timeout (H12)
- Boot timeout (R10/H20)
- Missing config vars or failed database connection
This guide also covers
- heroku application error
- heroku application error an error occurred in the application
- heroku app not working
- heroku 503 error
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