chrome · JavaScript
The message
TypeError: Failed to fetch
What it means
The request ended without a response, and the browser deliberately hides the reason: a CORS block, a dead address, a bad certificate, and an ad-blocking extension all produce these same two words. This is a thrown error rather than a status, so a 404 or a 500 never reaches it — the server never got as far as answering. There is often a second, more specific line just above it in the console or in the Network tab, so read that first, and hitting the URL with curl -i separates "the server is down" from "the browser refused". Firefox words the same situation as NetworkError when attempting to fetch resource.
The fix
curl -i https://api.example.com/data- Printed by
- chrome
- JavaScript
- 15
Browser and Node errors usually tell you what broke and not why the value became what it was — you read undefined, it was not a function, it was not JSON — so the place to fix is upstream of the line that threw, and silencing just that line with ?. and default values makes the same problem reappear further away in a form that is harder to recognise.
Reading an error message
- Read from the first line down. The lower you go the more it is about the tool’s internals; the cause is usually at the top.
- If there is a file and a line number, start there — not the top stack frame, but the topmost line that names a file you wrote.
- Search the message verbatim, but strip your own paths and variable names first; those are what stop the search from matching.
- The same condition is worded differently across tool versions. If results look wrong, add the version number to the query.
- Before pasting a fix, check what it throws away. Some of these cannot be undone.
Common questions
Q. What does “TypeError: Failed to fetch” mean?
The request ended without a response, and the browser deliberately hides the reason: a CORS block, a dead address, a bad certificate, and an ad-blocking extension all produce these same two words. This is a thrown error rather than a status, so a 404 or a 500 never reaches it — the server never got as far as answering. There is often a second, more specific line just above it in the console or in the Network tab, so read that first, and hitting the URL with curl -i separates "the server is down" from "the browser refused". Firefox words the same situation as NetworkError when attempting to fetch resource.
Q. How do I fix it?
curl -i https://api.example.com/data — before running it, check the explanation above for what this command discards.
Q. Which tool prints this?
chrome. It sits under JavaScript, and the message runs to 4 words.