Start an eID attempt in your own UI

Authenticate the user in your own interface instead of sajn’s hosted page. You show the QR code and the button that opens the eID app; sajn talks to the eID provider.

Flow:

POST /api/v1/login/sessions to create the session
POST here, from your server, with the user’s IP address. Show qrCode on desktop, or open autoStartUrl from a tap on mobile
POST /api/v1/login/sessions/{id}/poll every 1 to 2 seconds and show the new qrCode
When status is COMPLETED, read the result with GET /api/v1/login/sessions/{id}

Calling this again while an attempt runs returns that attempt. After a FAILED or EXPIRED attempt, calling it starts a new one while attemptsRemaining is above 0. The client must use your own BankID certificate.

POST

api

sessions

{id}

start

Start an eID attempt in your own UI

curl --request POST \
  --url https://app.sajn.se/api/v1/login/sessions/{id}/start \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "method": "SE_BANKID",
  "endUserIp": "192.0.2.10",
  "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15",
  "returnUrl": "https://example.com/logga-in"
}
'

import requests

url = "https://app.sajn.se/api/v1/login/sessions/{id}/start"

payload = {
    "method": "SE_BANKID",
    "endUserIp": "192.0.2.10",
    "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15",
    "returnUrl": "https://example.com/logga-in"
}
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({
    method: 'SE_BANKID',
    endUserIp: '192.0.2.10',
    userAgent: 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15',
    returnUrl: 'https://example.com/logga-in'
  })
};

fetch('https://app.sajn.se/api/v1/login/sessions/{id}/start', 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://app.sajn.se/api/v1/login/sessions/{id}/start",
  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([
    'method' => 'SE_BANKID',
    'endUserIp' => '192.0.2.10',
    'userAgent' => 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15',
    'returnUrl' => 'https://example.com/logga-in'
  ]),
  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://app.sajn.se/api/v1/login/sessions/{id}/start"

	payload := strings.NewReader("{\n  \"method\": \"SE_BANKID\",\n  \"endUserIp\": \"192.0.2.10\",\n  \"userAgent\": \"Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15\",\n  \"returnUrl\": \"https://example.com/logga-in\"\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://app.sajn.se/api/v1/login/sessions/{id}/start")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"method\": \"SE_BANKID\",\n  \"endUserIp\": \"192.0.2.10\",\n  \"userAgent\": \"Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15\",\n  \"returnUrl\": \"https://example.com/logga-in\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://app.sajn.se/api/v1/login/sessions/{id}/start")

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  \"method\": \"SE_BANKID\",\n  \"endUserIp\": \"192.0.2.10\",\n  \"userAgent\": \"Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15\",\n  \"returnUrl\": \"https://example.com/logga-in\"\n}"

response = http.request(request)
puts response.read_body

{
  "id": "cm4k2x9p10033abcd1234efgh",
  "method": "SE_BANKID",
  "qrCode": "bankid.67df3917-fa0d-44e5-b327-edcc928297f8.7.dd5bb5f5e2a4fbb09bc6eaaa0a5fd1f3e2a1b7d4e0c9f8a6b5d4c3b2a1908f7e",
  "autoStartToken": "7c40b5c9-fa74-49cf-b98c-bfe651f9a7c6",
  "autoStartUrl": "https://app.bankid.com/?autostarttoken=7c40b5c9-fa74-49cf-b98c-bfe651f9a7c6&redirect=null",
  "expiresAt": "2026-10-28T22:00:00.000Z"
}

{
  "code": "VALIDATION_FAILED",
  "message": "Invalid input: expected string, received undefined",
  "userMessage": "Förfrågan innehåller ogiltiga värden.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2",
  "issues": [
    {
      "path": "endUserIp",
      "code": "INVALID_TYPE",
      "message": "Invalid input: expected string, received undefined"
    }
  ]
}

{
  "code": "UNAUTHORIZED",
  "message": "Invalid API token",
  "userMessage": "Ogiltig API-nyckel",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "INSUFFICIENT_SCOPE",
  "message": "Insufficient OAuth scope: requires login:write",
  "userMessage": "Applikationen saknar behörighet (scope) för denna åtgärd.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2",
  "requiredScopes": [
    "login:write"
  ],
  "grantedScopes": [
    "profile:read"
  ]
}

{
  "code": "NOT_FOUND",
  "message": "Sajn Login session not found",
  "userMessage": "Resursen hittades inte.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2",
  "resource": "login_session"
}

{
  "code": "INVALID_STATE",
  "message": "The resource's current state doesn't allow the operation, such as editing a document that was already sent or downloading a file that isn't produced yet.",
  "userMessage": "Åtgärden är inte möjlig i resursens nuvarande status.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "RATE_LIMITED",
  "message": "API rate limit exceeded",
  "userMessage": "För många förfrågningar. Försök igen om en stund.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "INTERNAL_ERROR",
  "message": "Internal server error",
  "userMessage": "Något gick fel.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "UPSTREAM_UNAVAILABLE",
  "message": "A service the operation depends on, such as an eID provider or a connected integration, failed or is unavailable. Retry with exponential backoff.",
  "userMessage": "En extern tjänst svarar inte just nu. Försök igen om en stund.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

Authorizations

Authorization

string

header

required

API key, e.g. Authorization: Bearer sajn_svc_.... Not scope-limited: acts with its owner's workspace role.

Headers

Sajn-Version

enum<string>

API version for this request. Without it, the request uses the organization's default version; an organization without a default is pinned to the latest version by its first request.

Available options:

2026-09,

2026-10

Sajn-Workspace

string

ID of the workspace this request acts in, from GET /api/v1/workspaces. Without it, an API key acts in its default workspace. The token's user must be a member of the workspace; an OAuth token only accepts the workspace it was granted for. A workspace that doesn't exist or can't be reached returns 403 WORKSPACE_ACCESS_DENIED.

Idempotency-Key

string

Makes retries safe. A retry with the same key and the same request replays the stored response for 24 hours (header Idempotent-Replayed: true); the same key with a different request returns 400.

Maximum string length: 255

Path Parameters

string

required

The login session ID, from POST /api/v1/login/sessions.

Body

application/json

Body

endUserIp

required

The IP address of the person authenticating, as your server sees it. Never your server's own address.

Pattern: ^(?:(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])\.){3}(?:25[0-5]|2[0-4][0-9]|1[0-9][0-9]|[1-9][0-9]|[0-9])$

method

enum<string>

The eID to authenticate with, such as SE_BANKID. Leave it out when the client allows one method.

Available options:

SE_BANKID

userAgent

string

The user agent of the person's browser. It improves the eID provider's risk check and lets autoStartUrl return to the right browser.

Maximum string length: 1024

returnUrl

string

Where the eID app sends a user on the same device when they are done. Must be registered on the client. Leave it out and the user switches back by hand.

Response

200

string

required

The login session.

method

enum<string>

required

Available options:

SE_BANKID

qrCode

string | null

required

Render this as a QR code for a user on another device. It changes every second, so show the qrCode from each poll.

autoStartToken

string | null

required

Opens the eID app on this device if you build the link yourself. Null when the call resumed an attempt that was already running.

autoStartUrl

string | null

required

Open this on the user's device, from a tap, to launch the eID app. Null when the call resumed an attempt that was already running.

expiresAt

string<date-time>

required

When the user must have finished this attempt by.

Start an eID attempt in your own UI

curl --request POST \
  --url https://app.sajn.se/api/v1/login/sessions/{id}/start \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "method": "SE_BANKID",
  "endUserIp": "192.0.2.10",
  "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15",
  "returnUrl": "https://example.com/logga-in"
}
'

import requests

url = "https://app.sajn.se/api/v1/login/sessions/{id}/start"

payload = {
    "method": "SE_BANKID",
    "endUserIp": "192.0.2.10",
    "userAgent": "Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15",
    "returnUrl": "https://example.com/logga-in"
}
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({
    method: 'SE_BANKID',
    endUserIp: '192.0.2.10',
    userAgent: 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15',
    returnUrl: 'https://example.com/logga-in'
  })
};

fetch('https://app.sajn.se/api/v1/login/sessions/{id}/start', 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://app.sajn.se/api/v1/login/sessions/{id}/start",
  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([
    'method' => 'SE_BANKID',
    'endUserIp' => '192.0.2.10',
    'userAgent' => 'Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15',
    'returnUrl' => 'https://example.com/logga-in'
  ]),
  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://app.sajn.se/api/v1/login/sessions/{id}/start"

	payload := strings.NewReader("{\n  \"method\": \"SE_BANKID\",\n  \"endUserIp\": \"192.0.2.10\",\n  \"userAgent\": \"Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15\",\n  \"returnUrl\": \"https://example.com/logga-in\"\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://app.sajn.se/api/v1/login/sessions/{id}/start")
  .header("Authorization", "Bearer <token>")
  .header("Content-Type", "application/json")
  .body("{\n  \"method\": \"SE_BANKID\",\n  \"endUserIp\": \"192.0.2.10\",\n  \"userAgent\": \"Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15\",\n  \"returnUrl\": \"https://example.com/logga-in\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://app.sajn.se/api/v1/login/sessions/{id}/start")

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  \"method\": \"SE_BANKID\",\n  \"endUserIp\": \"192.0.2.10\",\n  \"userAgent\": \"Mozilla/5.0 (Macintosh; Intel Mac OS X 14_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/18.0 Safari/605.1.15\",\n  \"returnUrl\": \"https://example.com/logga-in\"\n}"

response = http.request(request)
puts response.read_body

{
  "id": "cm4k2x9p10033abcd1234efgh",
  "method": "SE_BANKID",
  "qrCode": "bankid.67df3917-fa0d-44e5-b327-edcc928297f8.7.dd5bb5f5e2a4fbb09bc6eaaa0a5fd1f3e2a1b7d4e0c9f8a6b5d4c3b2a1908f7e",
  "autoStartToken": "7c40b5c9-fa74-49cf-b98c-bfe651f9a7c6",
  "autoStartUrl": "https://app.bankid.com/?autostarttoken=7c40b5c9-fa74-49cf-b98c-bfe651f9a7c6&redirect=null",
  "expiresAt": "2026-10-28T22:00:00.000Z"
}

{
  "code": "VALIDATION_FAILED",
  "message": "Invalid input: expected string, received undefined",
  "userMessage": "Förfrågan innehåller ogiltiga värden.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2",
  "issues": [
    {
      "path": "endUserIp",
      "code": "INVALID_TYPE",
      "message": "Invalid input: expected string, received undefined"
    }
  ]
}

{
  "code": "UNAUTHORIZED",
  "message": "Invalid API token",
  "userMessage": "Ogiltig API-nyckel",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "INSUFFICIENT_SCOPE",
  "message": "Insufficient OAuth scope: requires login:write",
  "userMessage": "Applikationen saknar behörighet (scope) för denna åtgärd.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2",
  "requiredScopes": [
    "login:write"
  ],
  "grantedScopes": [
    "profile:read"
  ]
}

{
  "code": "NOT_FOUND",
  "message": "Sajn Login session not found",
  "userMessage": "Resursen hittades inte.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2",
  "resource": "login_session"
}

{
  "code": "INVALID_STATE",
  "message": "The resource's current state doesn't allow the operation, such as editing a document that was already sent or downloading a file that isn't produced yet.",
  "userMessage": "Åtgärden är inte möjlig i resursens nuvarande status.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "RATE_LIMITED",
  "message": "API rate limit exceeded",
  "userMessage": "För många förfrågningar. Försök igen om en stund.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "INTERNAL_ERROR",
  "message": "Internal server error",
  "userMessage": "Något gick fel.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

{
  "code": "UPSTREAM_UNAVAILABLE",
  "message": "A service the operation depends on, such as an eID provider or a connected integration, failed or is unavailable. Retry with exponential backoff.",
  "userMessage": "En extern tjänst svarar inte just nu. Försök igen om en stund.",
  "requestId": "req_V1StGXR8Z5jdHi6BmyT2"
}

Get started

Core concepts

Guides

Webhooks

API fundamentals

Upgrading

sajn Login

API reference

Start an eID attempt in your own UI

Authorizations

Headers

Path Parameters

Body

Response