Can I use one of these in an actual thrown error?

You can use the text, but the message alone isn't a real exception — you'd still need to throw it as your language's actual error type. It's meant for a mockup, a log-viewer sample or a screenshot, not for wiring into working error-handling code.

Exception Message Generator

Generates a plausible, fictional exception message — the kind of text an error-handling test, log viewer mockup, or documentation screenshot needs without pulling a real stack trace.

How many

Don't repeat what I've already seen

Your result will appear here.

What you'll get

This generator draws from a hand-checked list of 18 entries. Here is a spread of 6 of them, so you can see the style before you generate:

NullReferenceError: Cannot read property 'id' of undefined
ConnectionRefusedError: Could not reach service at port 5432
PermissionDeniedError: Caller lacks required 'write' scope
RateLimitExceededError: Too many requests in the last 60s
TokenExpiredError: Session token expired 4 minutes ago
SchemaMismatchError: Payload does not match expected shape

A fixed sample of the list, not a live draw — your own results are picked at random from all 18, without repeating until the list runs out. Original authoring for Generate Random — fictional, framework-neutral exception text.. Last reviewed 2026-07-18.

How to use this tool

Press generate for a message.
Generate again for a different one.

Common use cases

Error-handling UI mockups
Log-viewer test fixtures
Documentation screenshots

Limitations and good to know

18 fixed messages, framework-neutral by design — none of them is the literal text Java, Python, .NET or any other runtime would actually throw for that condition.
A single line only. No stack trace, file path or line number is generated alongside it.
These are display strings for a mockup, not thrown objects — nothing here can be caught in a try/catch, because nothing here runs any code.

Practical tips

A good message says what was expected as well as what happened; "invalid input" tells whoever reads the log nothing.
Never put user data or secrets in an exception message — it will end up in a log aggregator you do not control.

Entries are chosen with your browser's cryptographic random number generator, so every entry on the list is equally likely. How Generate Random works.

Frequently asked questions

Can I use one of these in an actual thrown error?: You can use the text, but the message alone isn't a real exception — you'd still need to throw it as your language's actual error type. It's meant for a mockup, a log-viewer sample or a screenshot, not for wiring into working error-handling code.