curl --request POST \
--url https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '
{
"key": "videos/clip.mp4",
"content_type": "video/mp4",
"storage_class": "STANDARD",
"metadata": {}
}
'import requests
url = "https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads"
payload = {
"key": "videos/clip.mp4",
"content_type": "video/mp4",
"storage_class": "STANDARD",
"metadata": {}
}
headers = {
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
body: JSON.stringify({
key: 'videos/clip.mp4',
content_type: 'video/mp4',
storage_class: 'STANDARD',
metadata: {}
})
};
fetch('https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'key' => 'videos/clip.mp4',
'content_type' => 'video/mp4',
'storage_class' => 'STANDARD',
'metadata' => [
]
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads"
payload := strings.NewReader("{\n \"key\": \"videos/clip.mp4\",\n \"content_type\": \"video/mp4\",\n \"storage_class\": \"STANDARD\",\n \"metadata\": {}\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"key\": \"videos/clip.mp4\",\n \"content_type\": \"video/mp4\",\n \"storage_class\": \"STANDARD\",\n \"metadata\": {}\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"key\": \"videos/clip.mp4\",\n \"content_type\": \"video/mp4\",\n \"storage_class\": \"STANDARD\",\n \"metadata\": {}\n}"
response = http.request(request)
puts response.read_body{
"upload": {
"upload_id": "2~tHc6Lc1fQy0Q",
"bucket": "my-app-assets",
"key": "videos/clip.mp4",
"created_at": "2026-01-15T09:30:00Z",
"content_type": "video/mp4",
"storage_class": "STANDARD",
"metadata": {}
}
}{
"error": {
"code": "UNAUTHORIZED",
"message": "Authentication required",
"request_id": "550e8400-e29b-41d4-a716-446655440000"
}
}{
"error": {
"code": "CONFLICT",
"message": "Resource with this name already exists",
"request_id": "550e8400-e29b-41d4-a716-446655440000"
}
}{
"error": {
"code": "IDEMPOTENCY_KEY_REUSED",
"message": "This Idempotency-Key was already used with a different request payload",
"request_id": "550e8400-e29b-41d4-a716-446655440000"
}
}Initiate a multipart upload
Stage an object as up to 10000 parts and assemble them in one step. Every part but the last must be at least 5 MiB, and no part may exceed 5 GiB — so an upload’s parts can hold far more than any object a caller would send through it.
The assembled object is written out in full when the upload is completed, and that write happens inside the completing request: budget for it at roughly 85 MiB/s, and note that the public edge ends any request at one hour. Objects beyond a few hundred GiB need a completion path this API does not offer yet.
curl --request POST \
--url https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads \
--header 'Authorization: Bearer <token>' \
--header 'Content-Type: application/json' \
--data '
{
"key": "videos/clip.mp4",
"content_type": "video/mp4",
"storage_class": "STANDARD",
"metadata": {}
}
'import requests
url = "https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads"
payload = {
"key": "videos/clip.mp4",
"content_type": "video/mp4",
"storage_class": "STANDARD",
"metadata": {}
}
headers = {
"Authorization": "Bearer <token>",
"Content-Type": "application/json"
}
response = requests.post(url, json=payload, headers=headers)
print(response.text)const options = {
method: 'POST',
headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
body: JSON.stringify({
key: 'videos/clip.mp4',
content_type: 'video/mp4',
storage_class: 'STANDARD',
metadata: {}
})
};
fetch('https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads', options)
.then(res => res.json())
.then(res => console.log(res))
.catch(err => console.error(err));<?php
$curl = curl_init();
curl_setopt_array($curl, [
CURLOPT_URL => "https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads",
CURLOPT_RETURNTRANSFER => true,
CURLOPT_ENCODING => "",
CURLOPT_MAXREDIRS => 10,
CURLOPT_TIMEOUT => 30,
CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
CURLOPT_CUSTOMREQUEST => "POST",
CURLOPT_POSTFIELDS => json_encode([
'key' => 'videos/clip.mp4',
'content_type' => 'video/mp4',
'storage_class' => 'STANDARD',
'metadata' => [
]
]),
CURLOPT_HTTPHEADER => [
"Authorization: Bearer <token>",
"Content-Type: application/json"
],
]);
$response = curl_exec($curl);
$err = curl_error($curl);
curl_close($curl);
if ($err) {
echo "cURL Error #:" . $err;
} else {
echo $response;
}package main
import (
"fmt"
"strings"
"net/http"
"io"
)
func main() {
url := "https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads"
payload := strings.NewReader("{\n \"key\": \"videos/clip.mp4\",\n \"content_type\": \"video/mp4\",\n \"storage_class\": \"STANDARD\",\n \"metadata\": {}\n}")
req, _ := http.NewRequest("POST", url, payload)
req.Header.Add("Authorization", "Bearer <token>")
req.Header.Add("Content-Type", "application/json")
res, _ := http.DefaultClient.Do(req)
defer res.Body.Close()
body, _ := io.ReadAll(res.Body)
fmt.Println(string(body))
}HttpResponse<String> response = Unirest.post("https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads")
.header("Authorization", "Bearer <token>")
.header("Content-Type", "application/json")
.body("{\n \"key\": \"videos/clip.mp4\",\n \"content_type\": \"video/mp4\",\n \"storage_class\": \"STANDARD\",\n \"metadata\": {}\n}")
.asString();require 'uri'
require 'net/http'
url = URI("https://storage.{region}.basaltic.sh/v1/buckets/{bucket}/multipart-uploads")
http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true
request = Net::HTTP::Post.new(url)
request["Authorization"] = 'Bearer <token>'
request["Content-Type"] = 'application/json'
request.body = "{\n \"key\": \"videos/clip.mp4\",\n \"content_type\": \"video/mp4\",\n \"storage_class\": \"STANDARD\",\n \"metadata\": {}\n}"
response = http.request(request)
puts response.read_body{
"upload": {
"upload_id": "2~tHc6Lc1fQy0Q",
"bucket": "my-app-assets",
"key": "videos/clip.mp4",
"created_at": "2026-01-15T09:30:00Z",
"content_type": "video/mp4",
"storage_class": "STANDARD",
"metadata": {}
}
}{
"error": {
"code": "UNAUTHORIZED",
"message": "Authentication required",
"request_id": "550e8400-e29b-41d4-a716-446655440000"
}
}{
"error": {
"code": "CONFLICT",
"message": "Resource with this name already exists",
"request_id": "550e8400-e29b-41d4-a716-446655440000"
}
}{
"error": {
"code": "IDEMPOTENCY_KEY_REUSED",
"message": "This Idempotency-Key was already used with a different request payload",
"request_id": "550e8400-e29b-41d4-a716-446655440000"
}
}storage:PutObject. See STORAGE permissions for the full list, what each one covers, and an example policy.Authorizations
An OAuth 2.0 bearer token, sent as Authorization: Bearer <token>.
This is the recommended way to authenticate.
Get one by exchanging a service account's access key pair at
POST /v1/oauth/token with grant_type=client_credentials. It is the
standard client-credentials grant, so any OAuth-aware library will
obtain and refresh it for you.
curl -s -u "$KEY_ID:$SECRET" -d grant_type=client_credentials \ https://iam.basaltic.sh/v1/oauth/token
Tokens last an hour by default. The same access key pair is separately your AWS SigV4 credential for the S3-compatible object endpoint, which speaks nothing else.
Headers
Optional client-generated key that makes a create replay-safe. Retrying a request with the same key returns the original outcome verbatim instead of creating a duplicate resource. Reusing a key with a different request body is rejected (422); a request whose key is still being processed returns 409. Records are honored for 24 hours. Use a UUID or similarly unique token.
255Path Parameters
"my-app-assets"
Body
Response
Multipart upload initiated.
Show child attributes
Show child attributes

