If you’re building B2B software, you generally have three practical options for SAML SSO:

1) Build SAML support yourself

You implement the SAML Service Provider (SP) side in your app.

What this involves

• Generating SAML auth requests
• Receiving and validating SAML assertions
• Handling certificate validation and signature checks
• Mapping SAML attributes to your user model
• Supporting IdP metadata, ACS URLs, entity IDs, logout, etc.

Pros

• Full control
• No external dependency/vendor
• Can fit your product exactly

Cons

• Easy to get wrong
• SAML is fiddly and security-sensitive
• Ongoing maintenance for edge cases, cert rotation, multiple IdPs, and customer-specific requirements

Best for

• Large engineering teams
• Companies expecting many enterprise SAML customers
• Teams willing to invest in security and support

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2) Use a third-party SSO/CIAM provider

Use a service that abstracts SAML for you, like:

• Auth0
• Okta
• OneLogin
• WorkOS
• Clerk / FusionAuth / Descope / etc. depending on your needs

What they provide

• SAML integration plumbing
• Admin dashboards / connection management
• Metadata and certificate handling
• Sometimes SCIM, OIDC, role mapping, just-in-time provisioning

Pros

• Much faster to ship
• Fewer security pitfalls
• Better for supporting multiple enterprise customers
• Often includes more enterprise features beyond SAML

Cons

• Added cost
• Vendor dependency
• Potential limitations/customization constraints

Best for

• Most B2B SaaS companies
• Teams that want to move quickly and avoid implementing SAML directly

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3) Support SSO indirectly through an IdP broker or identity platform

Instead of integrating directly with each customer’s IdP, you integrate with a broker/platform that connects to their identity systems.

Example pattern

Your app supports SSO via:

• OIDC with a broker, or
• SAML to one provider that then federates to customer IdPs

Pros

• Simplifies your app integration
• Can unify SAML, OIDC, SCIM, MFA, and directory sync

Cons

• Still a vendor dependency
• Less direct control over customer-specific IdP behavior

Best for

• Companies wanting enterprise identity features without building everything themselves

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Practical recommendation

For most B2B startups and SaaS products, the usual path is:

1. Start with a third-party provider
2. Support SAML SSO for enterprise plans
3. Add just-in-time provisioning and later SCIM if customers ask for lifecycle management
4. Only build SAML yourself if you have a strong reason to own it

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Things customers usually expect with SAML SSO

When customers say “we need SAML,” they often also expect:

• Enforced SSO for their domain
• JIT user provisioning
• Role/group mapping
• SP-initiated and sometimes IdP-initiated login
• Certificate rotation support
• Audit logs
• SCIM provisioning/deprovisioning

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Important design decision

You’ll want to decide whether SSO is:

• Per user login option, or
• Domain-enforced for a whole company

For B2B SaaS, domain-based organization mapping is common:

• user signs up with @customer.com
• admins configure SAML for customer.com
• all future logins for that domain redirect to the customer’s IdP

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Rule of thumb

• Need it quickly and safely? Use a provider.
• Need maximum control and have identity expertise? Build it.
• Need enterprise identity beyond SAML? Use a platform that also supports SCIM/OIDC.

If you want, I can also give you:

1. a build-vs-buy decision matrix,
2. a recommended architecture for SAML in a multi-tenant SaaS app, or
3. a vendor comparison for the common SSO providers.