# Newline Auth API

**Canonical:** https://apis.io/apis/fifth-third-bancorp/newline-auth-api/  
**Provider:** Fifth Third Bancorp — https://apis.io/providers/fifth-third-bancorp/  
**Base URL:** https://sandbox.newline53.com/api/v1  
**Documentation:** https://developers.newline53.com/reference/auth

Newline Auth API is one of 13 APIs that [Fifth Third Bancorp](https://apis.io/providers/fifth-third-bancorp/) publishes on the [APIs.io](https://apis.io/) network, described by a machine-readable OpenAPI specification. Tagged areas include Authentication, JWT, HMAC, and United States. The published artifact set on APIs.io includes an OpenAPI specification, API documentation, and an API reference.

Authentication for the Newline by Fifth Third platform. A client exchanges a refresh token for an access token by POSTing a JWS whose payload carries the Program UID (sub) and current epoch time (iat), signed with a previously shared HMAC using HS512. The returned access token (prefixed auth-) is valid for up to 8 hours and is supplied in the Authorization header of every subsequent request.

## Machine-readable artifacts (4)

- **OpenAPI** — https://raw.githubusercontent.com/api-evangelist/fifth-third-bancorp/refs/heads/main/openapi/newline-platform-api.json
- **Documentation** — https://developers.newline53.com/docs/api-authentication
- **APIReference** — https://developers.newline53.com/reference/post_auth
- **APIsJSON** — https://raw.githubusercontent.com/api-evangelist/fifth-third-bancorp/refs/heads/main/apis.yml

## Other Fifth Third Bancorp APIs (12)

- [Newline Customers API](https://apis.io/apis/fifth-third-bancorp/newline-customers-api/)
- [Newline Customer Products API](https://apis.io/apis/fifth-third-bancorp/newline-customer-products-api/)
- [Newline Products API](https://apis.io/apis/fifth-third-bancorp/newline-products-api/)
- [Newline Pools API](https://apis.io/apis/fifth-third-bancorp/newline-pools-api/)
- [Newline Custodial Accounts API](https://apis.io/apis/fifth-third-bancorp/newline-custodial-accounts-api/)
- [Newline Synthetic Accounts API](https://apis.io/apis/fifth-third-bancorp/newline-synthetic-accounts-api/)
- [Newline Transfers API](https://apis.io/apis/fifth-third-bancorp/newline-transfers-api/)
- [Newline Combined Transfers API](https://apis.io/apis/fifth-third-bancorp/newline-combined-transfers-api/)
- [Newline Transactions API](https://apis.io/apis/fifth-third-bancorp/newline-transactions-api/)
- [Newline Returns API](https://apis.io/apis/fifth-third-bancorp/newline-returns-api/)
- [Newline Virtual Reference Numbers API](https://apis.io/apis/fifth-third-bancorp/newline-virtual-reference-numbers-api/)
- [Newline Sandbox API](https://apis.io/apis/fifth-third-bancorp/newline-sandbox-api/)

## Tags

Authentication, JWT, HMAC, United States

---

Profiled by [API Evangelist](https://apievangelist.com) and published on [APIs.io](https://apis.io/apis/fifth-third-bancorp/newline-auth-api/). The API's provider profile, Kin Score and agent-readiness rating are at https://apis.io/providers/fifth-third-bancorp/.