An API that has been in production for years
Two interfaces, one account. A JSON API for the common operations, and a SOAP API that exposes the full campaign surface. Both authenticate with an API key from your account settings, and both can be restricted to specific IP addresses.
What you can do
Contacts
Create a contact, add it to a list, change its status. This is what most WordPress and CRM integrations call.
Transactional email
Send a single message to a single recipient, immediately, outside any campaign. Order confirmations, password resets, receipts.
Transactional SMS and OTP
Send a single SMS in real time. The usual case is a verification code your system generated and needs delivered in seconds.
Campaigns
Create and send a campaign programmatically through the SOAP interface, for systems that generate their own content.
JSON reference
Endpoint, function list, request and response shapes for the four JSON functions.
Security
API key in a header, plus an optional IP allowlist so the key only works from your servers.
Error codes worth knowing
0 success 1 invalid credentials or API key rejected 3 missing or malformed payload on a valid key
Code 3 is the one that confuses people: the key is fine, the request is not. Check that every required field is present, including the ones the documentation shows as empty strings.
Get an API key
Open a free account, then find the key under Advanced settings. If you need the IP allowlist configured, tell us the addresses.
Sign up freeContact usFrequently asked questions
Where do I get an API key?
In the account, under Advanced settings, in the API settings card. The same screen holds the IP allowlist.
JSON or SOAP?
JSON for contacts, single email and single SMS, which covers most integrations. SOAP when you need the full campaign surface.
Is there a rate limit?
Nothing published for normal use. If you are planning high-volume transactional sending, tell us the expected rate so we can size the account.
Can I restrict the key to my server?
Yes. The IP allowlist means a leaked key is useless from anywhere else.