What is it?
The Error Message Explainer turns cryptic errors into plain words. Paste an error and get what went wrong and the usual steps to fix it. It covers about 40 of the most common errors in JavaScript, Python, PHP, Java, SQL, npm, git and web servers.
Who is it for?
Students and beginners stuck on their first errors, bloggers seeing errors in theme code, junior developers, and anyone who copied an error from a log or console.
How to use it
- Copy the full error message (the first line is usually enough).
- Paste it.
- Read the explanation and try the fixes in order.
Examples it explains
- ReferenceError … is not defined: a variable or function doesn’t exist where it’s used; check spelling and that its script loads first.
- Cannot read properties of undefined: the object before the dot doesn’t exist yet; add
deferto scripts or check it first. - Unexpected token < in JSON: the server sent an HTML error page instead of JSON.
- Blocked by CORS: the other server doesn’t allow your site to read its response.
Never paste passwords, keys or private data from logs into any tool or forum.
Errors and how to fix them
- No match found: remove your own file names and numbers from the message, or paste just the error type (e.g. “TypeError: … is not a function”).
- Fix didn’t help: the same message can have several causes; check the line number in the original error first.
Open the tool: Error Message Explainer
Still stuck?
Contact support. Tell us which tool or page you were using, what you tapped, what you saw, and your phone or computer and browser (for example: Android phone, Chrome). We reply by email.
Questions, or an error not listed here?
Tell us in the comments: what you were doing, the exact message you saw, and your device and browser. We read every comment and add new fixes to this article.