Top 7 APIs for SaaS Development in 2026 (I’d Actually Use These)

7 APIs I’d Use in a SaaS in 2026

I've built enough small projects to learn one annoying lesson:

the code you don't want to write is usually the code that ends up taking the most time.

You start with a simple idea.

"I'll just build a SaaS that does X."

Then X needs Google OAuth.

Then it needs Stripe.

Then you need background jobs.

Then email.

Then some way to connect to your users' other tools.

Then analytics.

Three weeks later you've built everything except X.

So I started paying more attention to the services that handle this stuff for you.

Not random APIs that return the weather in London.

Actual infrastructure that can save you from spending a weekend building something nobody will ever pay you for.

Here are 7 I'd seriously consider using in a SaaS in 2026.

1. Nango

If you're building B2B SaaS, integrations are going to find you whether you like it or not.

You build a CRM.

Someone asks for HubSpot.

You add it.

Someone else asks for Salesforce.

Then Google Calendar.

Then Slack.

Then Microsoft.

And suddenly you're maintaining a collection of OAuth flows that you never wanted to maintain.

Nango is built for this.

It gives you a way to connect your application to third-party APIs without having to build every integration yourself.

They currently support hundreds of integrations, including a lot of the APIs you'd expect a B2B product to eventually need.

What I'd build

A tool for sales teams that connects to their existing stack and pulls everything into one place.

Something like:

HubSpot ─┐
Slack ───┤
Gmail ───┼──> Your SaaS
Calendar ─┤
Notion ───┘

The interesting product isn't "we connect to 900 APIs."

The interesting product is what you do with the information after you've connected them.

That's where I'd spend my time.

2. Firecrawl

I've written enough scraping code to know that scraping is one of those things that looks incredibly easy until you actually have to maintain it.

The first version is:

requests.get(url)

Cool.

Then the website uses JavaScript.

Then the HTML changes.

Then there's pagination.

Then Cloudflare.

Then you realize the page you need isn't even in the initial HTML.

Firecrawl is basically infrastructure for getting useful information from websites without having to build the whole scraping stack yourself.

You can crawl and scrape websites and get the result in formats that are actually useful for applications.

And there's a free tier to experiment with.

A SaaS I'd build with it

Competitor monitoring.

Give the app 5 competitors.

It checks their:

• pricing
• product pages
• changelog
• documentation
• blog

Then tells you when something changes.

Not:

"Here's a scraped website."

But:

"Your competitor increased their Pro plan from $49 to $69."

That's something a company might actually pay for.

3. Polar

Getting people to pay you is a surprisingly complicated engineering problem.

You don't just need a "Buy" button.

You eventually need subscriptions, customer management, invoices, webhooks, refunds, taxes, usage and a bunch of other things you didn't think about when you started.

Polar is interesting because it's built specifically around monetizing software.

And one thing I like about the direction they're taking is that they're thinking beyond checkout.

If your SaaS uses expensive infrastructure, knowing your revenue isn't enough.

You also want to know:

How much does this customer actually cost me?

That's a much more useful number.

Something I'd build

A simple revenue + infrastructure-cost dashboard for indie hackers.

Not another giant enterprise analytics platform.

Just:

MRR
Customers
Churn
Revenue / customer
Infrastructure cost
Actual margin

Because $10k MRR sounds great until you discover you're spending $8k serving those customers.

4. Trigger.dev

This is one of those services you don't really appreciate until you build something that needs it.

Let's say a user clicks:

Generate my report

Your application now needs to:

1. fetch data from several APIs
2. process it
3. generate a PDF
4. upload the PDF
5. send an email

You probably don't want one HTTP request sitting there doing all of that.

You want a background job.

Trigger.dev is built around this kind of work.

You can run long-running tasks, schedule them, retry them and build workflows without having to start by building your own job infrastructure.

A good use case

Automated reports.

Every Monday morning:

Fetch data
   ↓
Process it
   ↓
Generate report
   ↓
Save it
   ↓
Email customer

Nobody needs to be awake at 8 AM.

The application just does it.

This is the kind of infrastructure I like because it removes an entire category of problems instead of adding another feature to my stack.

5. Unkey

This one is mostly for people building APIs.

You launch an API.

You give users API keys.

Then you realize you need to answer questions like:

• How many requests did this customer make?
• What's their limit?
• Can I revoke their key?
• Who is abusing the API?
• What happens when they hit their quota?

You can build all of this yourself.

I wouldn't.

Unkey handles API keys, rate limits and usage-related infrastructure.

The SaaS idea

A developer-focused API platform where someone can:

Create API
    ↓
Generate keys
    ↓
Set limits
    ↓
Track usage
    ↓
Charge customers

The actual API is still yours.

Unkey just handles the part around it.

And honestly, this is exactly the kind of boring infrastructure I'd rather outsource.

6. Resend

Email is boring.

Which is exactly why I don't want to build it.

A SaaS needs emails for basically everything:

• verification
• password resets
• receipts
• notifications
• invitations
• reports
• alerts

Resend gives you an API for sending transactional email without making you deal with the usual email infrastructure headache.

The API is simple enough that sending an email can basically become:

await resend.emails.send(...)

That's what I want from infrastructure.

I don't want to think about it.

I want to send the email and go back to building my product.

The free tier is also enough to experiment with a small project before paying for serious volume.

7. PostHog

This is probably the one I'd install and forget about until I needed it.

Then six months later I'd realize it was one of the most useful things in the entire stack.

Because after you launch a SaaS, you start making guesses.

"Users probably want this."

"Nobody uses this feature."

"People are dropping off during onboarding."

Maybe.

Or maybe you're completely wrong.

PostHog gives you product analytics, session recordings, feature flags, experiments and other tools for understanding what's actually happening inside your product.

The free usage is pretty generous for a small project too.

The useful part

You can answer questions like:

1,000 people signed up

↓ 720 completed onboarding

↓ 310 used feature X

↓ 74 came back the next week

↓ 12 became paying customers

Now you have something to work with.

That's much better than sitting in a Discord server saying:

"I think users don't like the onboarding."

The stack I'd probably end up with

If I were starting a B2B SaaS tomorrow, I wouldn't necessarily use all seven.

But a stack could look something like:

Nango
  → integrations

Firecrawl
  → web data

Trigger.dev
  → background work

Unkey
  → API access

Resend
  → email

Polar
  → payments

PostHog
  → analytics

And that's kind of the interesting thing about building software in 2026.

You don't have to build every layer.

You can spend your time on the thing that makes your product different.

If you're building a CRM, don't spend two weeks building OAuth.

If you're building an API, don't spend a week writing rate limiting.

If you're building a reporting product, don't build your own job queue.

If you're building a paid product, don't reinvent billing.

Use the boring stuff.

Build the interesting stuff.

If I had to pick only 3

For a new B2B SaaS, I'd probably start with:

Nango integrations are painful.

Trigger.dev background work becomes necessary very quickly.

PostHog you need to know what users are actually doing.

The rest depends heavily on the product.

And that's probably the bigger lesson here.

Don't pick your stack because someone on X said it's the "2026 SaaS stack."

Pick it because you have a problem and someone already solved that problem better than you can solve it in a weekend.

That's a much better reason to add a dependency.

What are you using in your SaaS right now that you'd never build yourself?