Yes. The checking tools need no account. A gate is created without an account too, and is opened with a private link.

Is what I paste sent to a server?

No. The CSV validator, the JSON validator and the schema diff run in your browser. Only messages sent to a gate address reach the server, where they are kept for up to 7 days.

No. A contract here is a short list of fields with a type and a few limits. It covers the rules that receiving systems enforce most often, and it reads the same for CSV and JSON.

Stop bad payloads before they reach the other system

Two systems exchange data, one of them changes a field, and nobody notices until a customer does. Payload Gate checks each message against the format the receiver really accepts, and tells the sender exactly what is wrong.

The same message, with and without a gate

The receiving system stores labels of 30 characters at most. Edit the message and send it both ways.

Loading the tool…

Four tools, one contract

CSV validator
Check a file row by row before an import rejects it, or worse, accepts it.
JSON payload validator
Types, required fields, lengths and allowed values, on nested objects and arrays.
Schema diff
Compare two versions of a format and see which changes break existing senders.
Validation endpoint
An address of your own that checks every call and keeps a journal.

How a gate works

Describe the format. Fields, types, what is required, maximum lengths. Or paste a sample and let the tool propose it.
Get an address. One URL per gate. No account, no key to install.
Send through it. Each call is answered at once: accepted, or refused with the row, the field and the reason.
Read the journal. What came in, what was refused and why. Before changing the format, see which recent messages would stop passing.

When this is the right tool

A system sends data to another one, and neither can easily be changed.
The receiver truncates, rejects or mangles what does not fit, and says little about it.
The format changes over time: a shorter field, a new required column, a retired value.
Someone must be able to show what was sent and why it was refused.

What it does not do

The gate does not yet forward messages to a system of your own: the receiver behind it is simulated, and answers like a strict system that received the message. A message is limited to 64 KB, and a gate to 120 messages per hour. Do not send card numbers or health data. How it works explains how to put the same gate in front of a real system.

Questions

Is it free?: Yes. The checking tools need no account. A gate is created without an account too, and is opened with a private link.
Is what I paste sent to a server?: No. The CSV validator, the JSON validator and the schema diff run in your browser. Only messages sent to a gate address reach the server, where they are kept for up to 7 days.
Is this JSON Schema?: No. A contract here is a short list of fields with a type and a few limits. It covers the rules that receiving systems enforce most often, and it reads the same for CSV and JSON.