This page can be used to verify Saltpack messages online, without having to install the Keybase client. Saltpack was created by Keybase, and is described as "a modern crypto messaging format". The important part is this lets people easily sign or encrypt messages and share them in a browser-friendly format.
I was honestly a little surprised that I was unable to find any online message verifiers for Saltpack. If Keybase is going to advocate for a simplistic, modern crypto message format, ease of use and accessibility for newbies should be paramount. With this page, users will be able to verify a signed message they were given, without having to create or own a Keybase account themselves.
This page calls out to an AWS Lambda endpoint that contains a copy of the Keybase core executable. No authentication is required to verify messages using the Keybase client, so I simply verify the message and return the output. Your message is sent straight to the server, verified, and the output is shown and then thrown away. Both this website and the Lambda being called are open source, but use your own discretion when verifying sensitive information.
Your message should start with "BEGIN KEYBASE SALTPACK SIGNED MESSAGE." and end with "END KEYBASE SALTPACK SIGNED MESSAGE.". Make sure you copy the entire message, including the punctuation and excluding any trailing whitespace.