Send over HTTPS

POST a base64 encoded, already-signed Solana transaction to https://send.swqos.com/v1/transactions. The response is a receipt naming the signature, whether it was a duplicate, what you were charged, and your remaining balance.

The request#

POST https://send.swqos.com/v1/transactions with Content-Type: application/json and your bearer token. Bodies are capped at 8 KiB.

Field	Type	Meaning
`transaction`	string, required	Base64 of the serialized signed transaction. Legacy or versioned. At most 1232 bytes before encoding.

We forward the bytes unchanged. We do not re-sign, reorder, add a tip instruction, adjust a priority fee, or touch the transaction in any way. Whatever you serialize is what reaches the leader.

The receipt#

A successful submission returns HTTP 200 and this object.

Field	Type	Meaning
`signature`	string	The transaction signature, extracted from the bytes you submitted. It will always match what you signed.
`accepted`	boolean	True when the submission was forwarded and acknowledged upstream, or matched a recent duplicate.
`duplicate`	boolean	True when this signature was already accepted within the last 90 seconds. Not forwarded again and not charged.
`charged_lamports`	integer	What this submission cost. Zero for duplicates.
`balance_remaining_lamports`	integer	Your prepaid balance after this submission.

Anything other than HTTP 200 returns an error object with a code and a message. Every code is documented in errors, along with what causes it and how to fix it.

A complete example#

TypeScript

1const res = await fetch("https://send.swqos.com/v1/transactions", {
2  method: "POST",
3  headers: {
4    Authorization: `Bearer ${process.env.SWQOS_API_KEY}`,
5    "Content-Type": "application/json",
6  },
7  body: JSON.stringify({
8    transaction: Buffer.from(tx.serialize()).toString("base64"),
9  }),
10});
11 
12const { signature, charged_lamports } = await res.json();

Duplicates#

We deduplicate on your account plus the transaction signature for 90 seconds. Resubmitting the same signed bytes inside that window returns accepted: true, duplicate: true and charged_lamports: 0. Nothing is forwarded a second time and you are not charged again.

Racing submissions

If an identical submission is still in flight, the second one returns 409 SUBMISSION_IN_PROGRESS rather than being queued. Wait for the first to return instead of retrying immediately.

After the 90 second window the same bytes can be forwarded and charged again. By then the blockhash is usually expired, so resubmitting old bytes tends to cost 0.0002 SOL for a transaction that cannot land. Build a fresh transaction instead.

Reading the price#

The public default price is available without authentication. It is the global default, not your account’s effective price, so use /v1/account when the distinction matters.

pricing

1curl -sS https://send.swqos.com/v1/pricing
2 
3# {
4#   "submission_price_lamports": 200000,
5#   "billing_event": "accepted_submission",
6#   "refunded_when_not_landed": false
7# }

When to use HTTPS#

HTTPS is the right choice when you are adding swqos.com to an existing service, when your runtime makes raw QUIC awkward, or when a few milliseconds do not decide the outcome. It is a plain JSON POST and it works everywhere.

If latency is the reason you are here, use QUIC instead. Holding one connection open removes a TLS handshake and a TCP round trip from every single send.