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Cybersecurity · head to head

Clerk vs GNAT Pro

Clerk logo

Clerk

Cybersecurity

Drop-in user authentication and management for developers

From
Free
Free plan
Yes
Full reviewWebsite
GNAT Pro logo

GNAT Pro

Developer Tools

Software development environments and toolchains for Ada, C/C++ and Rust

From
On request
Free plan
No
Full reviewWebsite

The short version

  • Only Clerk has a free tier, so it costs nothing to try first.
  • Each has a real cost: Clerk pricing scales with monthly retained users, which can grow expensive quickly for consumer apps with large user bases.; GNAT Pro no pricing published on website; requires contacting AdaCore directly for quotes
  • Prices and features above were last checked on 29 August 2026.

Where they differ

Only the attributes on which Clerk and GNAT Pro actually diverge.

Attributes where Clerk and GNAT Pro differ
AttributeClerkGNAT Pro
Starting priceFreeOn request
Pricing modelfreemiumquote
Free tierYesNo
Platformsweb, ios, android, apiWeb
CategoryCybersecurityDeveloper Tools

Identical on both: user rating (Not yet rated).

What each one covers

Drawn from each product's published feature list. An absence here means we hold no record of it - not that the product lacks it.

Only in Clerk

  • Prebuilt UI components
  • Organization management
  • Multi-factor authentication
  • Social sign-on
  • Billing
  • Enterprise connections

Only in GNAT Pro

Nothing recorded that Clerk does not also cover.

What people use each for

The jobs each tool is most often brought in to do.

Clerk

  • Adding sign-in and user profiles to a web or mobile app quicklynot GNAT Pro
  • B2B SaaS apps needing organizations and role-based accessnot GNAT Pro
  • Startups wanting prebuilt UI instead of building auth in-housenot GNAT Pro
  • Apps needing MFA and fraud detection out of the boxnot GNAT Pro

GNAT Pro

  • Building certified avionics software meeting DO-178B/C standardsnot Clerk
  • Developing automotive embedded systems with ISO-26262 compliancenot Clerk
  • Integrating Ada, C/C++, and Rust components in single codebasenot Clerk
  • Managing software supply chain vulnerabilities and SBOMsnot Clerk
  • Supporting long-lived software systems spanning decadesnot Clerk

Where each one falls short

Documented limitations, not opinions. Every one is a constraint you would hit in normal use.

Clerk

  • Pricing scales with monthly retained users, which can grow expensive quickly for consumer apps with large user bases.
  • Enterprise SSO connections beyond the first are billed as add-ons, adding cost for larger organizations.
  • The Business tier's extra dashboard seats cost $20/month each, which adds up for larger teams.
  • Enterprise-tier features like the 99.99% uptime SLA require annual contracts rather than flexible monthly billing.

GNAT Pro

  • No pricing published on website; requires contacting AdaCore directly for quotes
  • Vendor indicates per-user, per-year subscription model but does not disclose specific costs

Pricing, plan by plan

Clerk

Free
  • HobbyFree
    • 50,000 MRU limit per app
    • Up to 3 dashboard seats
    • Unlimited applications
  • Pro$25/month
    • 50,000 MRUs included, $0.02/MRU overage
    • Up to 3 dashboard seats
    • 1 Enterprise Connection included
  • Business$300/month
    • 50,000 MRUs included with volume pricing
    • 10 dashboard seats included
    • SOC2 report and priority support
  • Enterprise$undefined/month
    • Custom pricing, annual billing
    • 99.99% uptime SLA
    • HIPAA available, dedicated Slack channel

GNAT Pro

On request

No published plan breakdown. See the GNAT Pro review.

Which should you pick?

Choose Clerk if

  • You need prebuilt ui components.
  • You want to start without paying.
  • You work on web, ios, android, api.
  • You also want organization management.
Clerk review

Choose GNAT Pro if

Nothing in the data separates GNAT Pro from Clerk on the points above - pick on price and on how each one feels to use.

GNAT Pro review

Questions people ask

Is Clerk or GNAT Pro better?
Neither clearly leads. Clerk starts at Free and GNAT Pro at On request, and user ratings are close enough to be indistinguishable. Choose on capability and platform support.
Which is cheaper, Clerk or GNAT Pro?
Clerk has a free tier; the other does not. Paid plans start at Free for Clerk and On request for GNAT Pro.
Does Clerk or GNAT Pro run on more platforms?
Clerk runs on web, ios, android, api. GNAT Pro runs on Web.
Can I use Clerk for free?
Yes. Clerk has a free tier, so you can try it without paying. GNAT Pro starts at On request.
What is Clerk best used for?
Clerk is most often used for adding sign-in and user profiles to a web or mobile app quickly, b2b saas apps needing organizations and role-based access, startups wanting prebuilt ui instead of building auth in-house, apps needing mfa and fraud detection out of the box. Of those, adding sign-in and user profiles to a web or mobile app quickly and b2b saas apps needing organizations and role-based access are not what GNAT Pro is typically brought in for.
What can Clerk do that GNAT Pro cannot?
Clerk covers Prebuilt UI components, Organization management, Multi-factor authentication, Social sign-on.

Answered from the vendors’ own pages

Clerk: What does Clerk cost?

Clerk's Hobby plan is free with a 50,000 MRU limit; Pro is $25/month ($20/month billed annually), Business is $300/month ($250 annually), and Enterprise uses custom annual pricing.

Source
GNAT Pro: How much does GNAT Pro cost?

GNAT Pro pricing is not published on the website. Customers must request a pricing quote by contacting AdaCore directly or speaking with a GNAT Pro expert.

Source
Clerk: Is there a free plan and what are its limits?

Yes, the Hobby plan is free with a 50,000 monthly retained user (MRU) limit per app, up to 3 dashboard seats, and unlimited applications, with no credit card required.

Source
GNAT Pro: What is GNAT Pro licensing model?

GNAT Pro is sold on a per-user, per-year basis with no license locks. Customers can request pricing for their specific needs.

Source
Clerk: How is usage metered?

Clerk meters by monthly retained users (MRUs) — users who return to the app at least a day after signing up — with overage billed at $0.02 per MRU beyond the included 50,000 on paid plans.

Source
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