Sending SMS#
Each API key may have a limited number of send calls in progress at the same time. The limit counts calls
that are running, not calls per second. It covers /api/SendSMS, /api/SendSMSMulti and /api/Verify, in
both their POST and GET forms.When you are over the limit, a new call first waits a few seconds for a free place. If none frees up, it is
refused:HTTP/1.1 429 Too Many Requests
Retry-After: 5
{"Data": [], "ErrorMessages": ["Too many concurrent requests. Retry in 5s."]}
Retry-After and send it again.How to send in volume without meeting the limit:Keep a fixed number of connections open and send over them one call after another. A handful of parallel
connections carries a lot of traffic, because each call answers quickly.
Do not open a new connection for every message and do not fire all your messages at once.
On 429, slow down: wait Retry-After seconds, then continue with fewer parallel calls. Do not retry at once
in a loop.
Set your HTTP time-out to 30 seconds or more, so a call that is waiting for a place is not cut off by your
side.
Signing in#
The sign-in call is limited to 20 calls per 5 minutes per IP address. Above that it answers 429 with the message
Too many login attempts. Please try again later. and no Retry-After header. Sign in once, keep the token and
renew it with the refresh call (see Authentication).Other calls#
The other calls have no published limit today. Please page through lists with a reasonable page size and do not
poll faster than you need. For delivery results, a delivery report sent to your server is
better than asking again and again.Modified at 2026-10-08 10:41:52
