Open source auth providers in 2025: best solutions for open source auth in SaaS
Best open source auth providers in 2025
Open source software is better for developers. It’s transparent, flexible, and stable. You're not locked into someone else’s roadmap — or their pricing model. And in many cases, open source is just... better.
Nowhere is that more true than in authentication. If you're building something serious — especially for enterprise — proprietary auth platforms can feel brittle, black-boxed, and bloated. Many teams want something they can fully control. Something they can self-host, audit, and extend.
In this guide, we’ll walk through the best open source auth providers available in 2025. Some are huge, mature platforms with every feature under the sun. Others are newer, leaner, and built for modern workflows. Whatever you're building — there's probably a good fit here.
Keycloak
What is Keycloak?
Keycloak is, by now, the default answer for open source identity and access management. It's been around a fairly long time. It's been battle-tested in countless real environments.
Over the years, Keycloak has ballooned in functionality. It's not really for anyone in particular; it's used by enterprises, small companies, and even hobbyists. It's really a project that tries to do everything. That's good in some cases and bad in others.
If you're an expert in identity willing to do battle with lacking documentation and legacy software, you may have a good experience. Make no mistake: Keycloak is extremely powerful! You can contort its behavior to suit practically any application.
But that means Keycloak is extremely complex. If you go with Keycloak, you just need to know what you're signing up for. Your life is just not going to be very easy. If you're looking for something straightforward and opinionated that has minimal maintenance obligations, Keycloak simply is not right for you.
I can't possibly hope to enumerate everyone's opinions about Keycloak here. Some people really do love it. Others wonder why anyone uses it. I'd encourage you to explore for yourself. Nonetheless, I'll try to illustrate the sentiments that developers have relayed to me -- using similar public comments available on the internet.
On Hacker News:
We use Keycloak a lot at work, with many public and private instances. It is an amazing product and I keep discovering features every day... I feel like there’s a good need for a UX expert in the team because it seems that Keycloak is becoming one of those pieces of software we pay consultants to come and explain to us, because it is cheaper than us doing it by reading the manual and trying different combinations
On Hacker News:
My boss recently called Keycloak "the gift that keeps on giving", but he was actually commenting on how there's a new ticket in jira for figuring out how the f*?k to do something. Having said that, I have terraform that creates an EKS cluster, deploys Keycloak , creates clients (SAML/OIDC), adds external identity providers, sets up an AWS IAM Identity Provider for it etc. That makes it extremely easy to use once you've figured out (a) what it can do, (b) how to do it in the ui, (c) how to get mrparkers Terraform provider to do it for you.
On Hacker News:
I went with using Keycloak for a platform I'm developing right now and it feels like a very overcomplicated enterprise piece of software - it still does work and has the features that I need (notably: an SSO login portal, user registration, password resets and social login), but definitely needed a certain amount of time to configure correctly and had odd bugs ... It works, but I'm still not happy.
On Hacker News:
[Keycloak is] on my list of things that assumes out of the box that you know waaaaaay more about dozens of details than you actually are likely to unless you've already used it for 10 years. To the point that I don't even know what the benefit of using it vs. other options is at all.
Up to you whether it's a fit!
Authentik
What is Authentik?
Authentik is a modern open source identity provider written in Python. It’s pitched as a simpler alternative to Keycloak, with a cleaner UI and more manageable codebase. For what it's worth, I can confirm that Authentik is way easier to set up. It literally took me about three minutes to spin up a functional Authentik instance locally. (Keycloak can be a bit of a beast!)
Note that Authentik is primarily a corporate identity provider -- used for workforce identity more than customer identity.
It supports all the usual features you'd want from a corporate identity provider — SSO, LDAP, SAML, OIDC, MFA, etc. It's quite popular among companies who want something more manageable than Keycloak. Moreover, I've started to see some real enterprises deploy Authentik in lieu of more established IDPs like Okta and Microsoft Entra.
Why did I include Authentik in this list? Well, it's a bit like Okta in that you can use it as more of an identity broker to implement auth in SaaS. It's not really what Authentik is best at, but you can indeed use the product that way!
Here are some comments on the public internet that roughly illustrate what I've heard firsthand from developers; these comments can't possibly hope to describe the full universe of experiences, though.
On Hacker News:
Using Authentik as a part of my selfhosted setup, mostly positive things to say. I tried with Keycloak first but had too much trouble getting the Docker image to work, so switched to Authentik ... Ultimately, I've gotten at least somewhat familiar with all the complexities of Authentik, so I'd have a hard time switching off. Would definitely love to see a solution geared towards selfhosting that's more barebones, though.
On Reddit, a few years back:
I’m impressed enough [with Authentik] that I actually have hope it’ll be a viable professional alternative to keycloak - keycloak works great but it’s a very big lift and learning curve, especially for greener teams to maintain and troubleshoot. I can’t recommend it for production use before it gets some security audits under its belt, but those are hyper expensive and it’s still a fairly young product
Might be a good fit if you're basically looking for Keycloak, but simpler.
Ory
What is Ory?
Ory is a suite of open source identity services, modular by design. Ory comprises a few separate components: Oathkeeper for login; Kratos for identity; and Keto for access control, for example.
You're on the hook to wire them together based on what you need. It’s API-first, dev-focused, and well-documented. It's a really great set of tools if you really know what you're doing, but be aware that you're opting into complexity. Expect to do some work.
I'd consider it a more modern solution Keycloak peer. Ory does have a major advantage over Keycloak: you can use the Ory Network as a fully managed solution. At minimum, this is usually a better place to start than self-hosting.
Here are a few things people have said about Ory:
I learned so much about AuthN and AuthZ from reading Ory code and docs. Sometimes it seems like Ory is the only web auth stuff on the internet that’s intended for you to understand how the whole system works, rather than telling you just enough to get you to use/buy their proprietary software (Auth0, Okta, etc).
Keycloak is much heavier than Hydra. With Hydra, it is much easier to spin up thin OpenID clients. If one has a need to spin up dozens or hundreds of OpenID clients, Hydra will be definitely a better choice purely because one can have multiple Hydra servers running with only a handful of clients each. Think multi tenant environments. With Hydra, there is no reason not to have many Hydra instances with as low as a single OpenID client ... What speaks for Keycloak is the completness: user and role management, permissions, resource servers and so on. However, if one wants just tokens and does not mind writing the glue code to Kratos and Keto, Ory stack is awesome.
Tesseral
What is Tesseral?
Tesseral, launched in 2025, is a new open source authentication platform purpose-built for B2B SaaS. It rethinks the typical auth stack from first principles — with sane defaults, enterprise features out of the box, and elegant developer experience. It’s designed for SaaS applications that need to support orgs, users, roles, and complex auth flows — without wrestling with ancient software.
Because Tesseral focuses relatively narrowly, it can deliver rich functionality without the complexity you'll run into with other open source projects. With just a few lines of code, you can set up B2B multitenancy, multi-factor authentication, SAML SSO, enterprise OIDC, fine-grained access control, SCIM provisioning, and more. It's remarkably powerful given how little work it takes to implement.
You pretty much just have to wrap your frontend like this:
npm install @tesseral/tesseral-react
import { createRoot } from "react-dom/client";
import { TesseralProvider } from "@tesseral/tesseral-react";
const root = createRoot(...);
root.render(
// see below for how to get your publishableKey
<TesseralProvider publishableKey="publishable_key_...">
<App />
</TesseralProvider>
);
And then you add some minimal backend code like this (using Flask as an example):
from flask import Flask
from tesseral_flask import require_auth
app = Flask(__name__)
app.before_request(require_auth(publishable_key="publishable_key_..."))
That's pretty much it!
Tesseral is the newest and most rapidly developing player in the space. Come learn more about what we're building! You can even book a meeting with me directly if you're curious!
