Error: authentication state mismatch

Is anyone having trouble authenticating to the Monzo Developer Portal (to get an api key)? This used to work for me, but when I try now, after clicking on the authentication link the email I receive, I get:

Error: authentication state mismatch


Not sure what to do, any advice appreciated!

It’s working now. Obviously when I encounter an error, I should post on the forum and that provides the requisite amount of time for it to resolve!

Any insight from Monzo staff (or others) would still be of interest, in case it happens again.

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I’m seeing this same issue at the moment - “Authentication state mismatch”, after requesting an API key. Tried it many times. Did it just fix itself for you?

Sorry I didn’t see this earlier, but yes, it just fixed itself for me. Hopefully working for you now? @simon do you have any ideas as to why this happens?

Hey, I tried to create a developer account yesterday and now as well, and I got this error both times. Can somebody please help with it?

I am also receiving this error as well…

Still getting it, any help would be appreciated.

Also getting the same error trying to sign up for a key today. Any help?

I found this error occurred when clicking the magic link on a different device than that one that requested it.

You’re right - clicking through the email on my laptop worked. Slightly confusing as the prompt says phone. Thanks!

I think they reuse the magic link for app sign in?

I’m getting this error again :confounded:. No idea why, as I’m requesting the magic link on my laptop and going to Mail and clicking the email link on the same machine. Does anyone know what else could cause this?

Is your mail client opening up in a different browser? The only reason I ask is that when you submit your email, the state may be getting stored in a session. When you click that link, it would be checking that session again to match against the URL state.

Thanks for the response, and sorry to take so long to update this. To answer your question, I was using the same browser to request the link and then open it (I actually tried with both Safari and Firefox, being consistent each time). But I think I’ve found why I was having trouble. I was opening the following URL directly:

This is from a script I use to add notes to transactions, and it has the URL hard-coded into the script. That URL was from the redirect I got when clicking on Sign in with your Monzo account from This used to work for me. However, I think this is now what’s causing the state mismatch. When I started directly from, it all worked fine. I’ve now changed the URL in the script to:

and all works as expected.

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