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POST
cURL (Windows)
The playground on this page is live. There is no test mode and no sandbox: pressing Send authenticates with the key you paste and really calls https://api.bulkneo.com — a send delivers a real WhatsApp message to the number you type, and an instance call really changes your account. Use your own number while you are exploring, and paste a key only from a machine you trust.Your browser remembers what you type into the playground, so a key you paste here is still in the Authorization box on your next visit. Nobody else sees it — it never leaves your machine and it is not part of this site — but on a shared or borrowed computer, clear the site data when you are done.
Acknowledge a message with a 👍 instead of sending another one.

Notes

  • message_id is the message you are reacting to. For a message you sent, that is the data.message_id you got back from the send.
  • Set from_me: true when reacting to a message you sent from this number. It defaults to false, meaning a message the contact sent you, and it cannot be worked out from the id alone — which is why it is a separate field.
  • emoji must be a single emoji with no spaces, up to 24 characters (a multi-part emoji such as 👨‍👩‍👧 counts as several).
  • Send "emoji": "" to remove a reaction you added earlier. That is WhatsApp’s own behaviour, not a validation gap.
  • This is the only send type that does not accept quoted_message_id — the message key already identifies the conversation.

Add a reaction

Remove it again

You can only react to messages this API knows the id of — in practice, messages you sent. There is no way to receive incoming messages or their ids. See What is not available yet.

Authorizations

apikey
string
header
required

Your API key, sent in an apikey request header. Never in the URL, never as a Bearer token.

Headers

Idempotency-Key
string

OPTIONAL. A unique string you choose, 8-255 characters of letters, digits or . _ : ~ -

Send the same key with the same body again within 24 hours and the ORIGINAL result is returned without sending a second message — which is what makes a network retry safe. A different body on the same key is refused with 422 idempotency_key_reused rather than silently overwriting either result.

Responses carry Idempotency-Replayed: true|false while this is active. If that header is ABSENT, idempotency is not enabled on this deployment and retries will send again.

Required string length: 8 - 255
Pattern: ^[A-Za-z0-9._:~-]{8,255}$

Body

application/json
instance_id
string<uuid>
required

Which of your connected numbers to send FROM. Copy it from your numbers screen in the portal, or from GET /v1/instances. It must belong to your account.

Example:

"3f9c1a2b-7d4e-4c81-9f0a-2b6d5e8c1a34"

to
string
required

The recipient, with country code and no leading zero — for example 919000000000. Spaces, dashes, brackets and a leading + are accepted and stripped; 6 to 15 digits must remain.

Example:

"919000000000"

message_id
string
required

The message to react to — the data.message_id returned when it was sent. Letters, digits, _, =, +, / and - only.

Maximum string length: 128
Example:

"3EB0C1D2F4A5B6C7D8E9"

emoji
string
required

A single emoji with no spaces. Send an empty string to REMOVE a reaction you added earlier — that is WhatsApp's own behaviour, not an error.

Maximum string length: 24
Example:

"👍"

from_me
boolean
default:false

Set true when reacting to a message you sent from this number. Defaults to false (a message the contact sent you).

Response

Accepted for delivery. data.type is always reaction on this endpoint.

success
boolean
data
object
request_id
string<uuid>