# SAML vs OIDC: Which Federation Protocol Should You Use?

Source: https://startwithidentity.com/guides/fundamentals/saml-vs-oidc/
Last updated: 2026-08-29
License: content by Start with Identity. Cite the source URL.

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SAML and OpenID Connect (OIDC) both enable single sign-on, but they come from different eras and fit different jobs. Choosing well saves you years of integration pain.

## SAML 2.0

SAML is an XML-based standard from 2005, deeply entrenched in **enterprise web SSO**. If you sell to enterprises, you will be asked for SAML, because that is what their identity providers speak. It is mature and universally supported, but XML and its signing rules are heavy and error-prone.

## OpenID Connect (OIDC)

OIDC is a modern identity layer built on top of [OAuth 2.0](https://startwithidentity.com/guides/fundamentals/oauth-vs-oidc/), using JSON and JWTs. It is the better fit for **mobile apps, single-page apps, and APIs**, with simpler tokens and a cleaner developer experience.

## How to choose

- Building consumer or developer-facing apps, mobile, or APIs: prefer **OIDC**.
- Integrating with enterprise customers or legacy IdPs: you will likely need **SAML** too.
- Most [CIAM](https://startwithidentity.com/vendors/ciam/) and [IAM](https://startwithidentity.com/vendors/iam/) platforms support both, so the real question is which your counterparties require.

## The security difference nobody mentions

SAML's security record is worse than OIDC's, and the reason is structural rather than reputational. Validating an XML signature correctly is genuinely hard: canonicalization, parser differentials between the library that validates and the library that reads, and assertion wrapping have produced a long run of authentication bypasses where a service provider accepted a forged assertion as valid.

The August 2026 miniOrange SAML plugin flaws are a clean example. The validation function performed a loose boolean check on the tri-state integer PHP's `openssl_verify()` returns, so the error value of -1 read as success. An attacker sent a deliberately malformed signature, triggered an OpenSSL error, and signed in as WordPress administrator. The cryptography worked perfectly; the calling code asked the wrong question.

If you operate a SAML service provider, audit for exact-match comparison on verification results, reject unexpected signature algorithms rather than falling through, pin the expected signing certificate, and check that the assertion is addressed to you, is recent, and has not been replayed. See the [identity CVE catalog](https://startwithidentity.com/cves/) for how often this class recurs.

OIDC is not immune, and its equivalent failure modes are [JWT](https://startwithidentity.com/glossary/jwt/) validation errors: accepting `alg: none`, confusing HMAC and RSA verification, skipping the audience check, or trusting a `kid` that points at attacker-controlled key material. The difference is that a maintained JWT library with pinned algorithms closes most of them, while XML signature validation has more places to go wrong.

## Practical implementation notes

- **You will support both.** Any B2B SaaS selling upmarket needs SAML because enterprise buyers require it, and needs OIDC because that is what your own application uses. Plan for both rather than picking.
- **SCIM is a separate question.** Federation gets a user logged in; it does not create or remove the account. [SCIM](https://startwithidentity.com/standards/scim-2-0/) handles [provisioning](https://startwithidentity.com/glossary/provisioning/), and enterprise buyers usually ask for both together.
- **Metadata and certificate rotation** are the operational tasks that break SAML integrations in production. Automate metadata refresh where the partner supports it.
- **OIDC discovery** lets a client self-configure from one well-known URL, which is the practical superpower and why new integrations are faster.

## Where to start

See our [SSO implementation guide](https://startwithidentity.com/guides/authentication/complete-guide-implementing-sso/) and [federation providers](https://startwithidentity.com/vendors/iam/). For the OAuth relationship, read [OAuth vs OIDC](https://startwithidentity.com/guides/fundamentals/oauth-vs-oidc/).