W3SpeedUp Critical CSS API:
W3SpeedUp’s Critical CSS API is a developer tool that automatically generates critical CSS for any URL, with no headless browser setup and no manual stylesheet sorting. Load faster, rank higher, and impress users from the first pixel.
Prioritize First Load
Our Critical CSS API renders your page, detects what loads first, and generates the Critical CSS automatically. You don’t have to sort through stylesheets or tweak anything. It gives you exactly what is needed for faster first paint.
Deliver Fast Themes
If you build templates or themes, then use this API for Critical CSS and help yourself embed critical CSS into each one automatically. You give your users speed by default, without asking them to optimize anything.
Boost Build Performance
You can employ our API in your build or deploy process to generate critical CSS for every page, on the go. That means actual good news; as your whole project stays fast, no matter how big it gets.
Supports All Frameworks
Our online critical CSS API doesn’t care what framework you use, be it React, Vue, static sites, or anything else. The reason is that, as a user, you just send a URL and get clean, critical CSS ready to drop in.
Skip Browser Setup
You know the best part about our creation is that there is no need to run headless browsers or maintain custom scripts if you have this API. Yes, we are serious. It automates the real task behind critical CSS extraction and saves you time.
Made for Smart Builders
Building a CMS, a site builder, or a performance tool has never been easier with this CSS critical path API. It helps you deliver speed without building the logic from scratch, and you get reliable output with zero hassle.
Who the Critical CSS API is for
Automated critical CSS for a URL
Best for: Developers and technical teams who need above-the-fold CSS for a URL without running their own headless browser. The page says you send a URL and get critical CSS back.
Ideal for: Any site, including React, Vue, or static builds, that can be reached by URL.
Choose this if: You want the first paint improved and you do not want to maintain a browser farm.
Theme and template builds
Best for: Theme and template authors who want critical CSS embedded so customers get a faster first paint without optimizing it themselves. That is the “Deliver Fast Themes” use on this page.
Ideal for: A theme shop or a template kit with many layouts.
Choose this if: Speed has to be the default in what you ship, not a step you ask each user to do.
Build and deploy pipelines
Best for: Developers who want critical CSS generated during build or deploy so new pages stay fast as the project grows. That is the “Boost Build Performance” use on this page.
Ideal for: A CI pipeline or a static-site deploy.
Choose this if: You already ship from a build step and want this call added there.
CMS, site-builder, and performance products
Best for: Teams building a CMS, a site builder, or a performance tool who want critical CSS without writing the extraction logic. That is the “Made for Smart Builders” use on this page.
Ideal for: A product that manages many customer websites.
Choose this if: You need reliable output for other people’s sites, not a one-page experiment.
Who each Critical CSS API plan is for
Free
Best for: Developers testing critical CSS generation, or a single small site. The Free card lists 50 Credits every Month and Upto 1000 request every hour.
Ideal for: Evaluating the API before you commit to a paid allowance.
Choose this if: Your volume fits 50 Credits every Month and Upto 1000 request every hour.
Choose a higher plan if: You need 1000 Credits every Month and upto 40 request every minute, which Hobby lists and this card does not.
Hobby
Best for: Indie developers and small theme or template projects. The Hobby card lists 1000 Credits every Month and Upto 40 request every minute.
Ideal for: A theme, a few client sites, or a small deploy.
Choose this if: Your volume fits 1000 Credits every Month and Upto 40 request every minute.
Choose a higher plan if: You need 6000 Credits every Month and upto 60 request every minute, which Startup lists and this card does not.
Choose a lower plan if: 50 Credits every Month and upto 1000 request every hour is enough. That is what Free lists.
Startup
Best for: Agencies and build pipelines that generate critical CSS for more URLs. The Startup card lists 6000 Credits every Month and Upto 60 request every minute.
Ideal for: A multi-site agency workflow or a growing static build.
Choose this if: Your volume fits 6000 Credits every Month and Upto 60 request every minute.
Choose a higher plan if: You need 15,000 Credits every Month and upto 120 request every minute, which Business lists and this card does not.
Choose a lower plan if: 1000 Credits every Month and upto 40 request every minute is enough. That is what Hobby lists.
Business
Best for: Site builders, CMS products, and teams generating critical CSS across many pages. The Business card lists 15,000 Credits every Month and Upto 120 request every minute.
Ideal for: A product that generates critical CSS for many customer sites.
Choose this if: Your volume fits 15,000 Credits every Month and Upto 120 request every minute.
Choose a lower plan if: 6000 Credits every Month and upto 60 request every minute is enough. That is what Startup lists.
This table compares the Start Free, Upgrade Anytime options already listed on this page. Each column is one plan card. Prices, limits, and inclusions are copied from those cards only.
| Comparison item | Free | Hobby | Startup | Business |
|---|---|---|---|---|
| Current price on the card | 0 USD, Monthly Cost | 9 USD, Monthly Cost | 29 USD, Monthly Cost | 99 USD, Monthly Cost |
| Crossed-out price shown on the card | 100 USD | 100 USD | 100 USD | 100 USD |
| 50 Credits every Month | Listed | — | — | — |
| Upto 1000 request every hour | Listed | — | — | — |
| 1000 Credits every Month | — | Listed | — | — |
| Upto 40 request every minute | — | Listed | — | — |
| 6000 Credits every Month | — | — | Listed | — |
| Upto 60 request every minute | — | — | Listed | — |
| 15,000 Credits every Month | — | — | — | Listed |
| Upto 120 request every minute | — | — | — | Listed |
| Pricing link on the card | https://rapidapi.com/ashishphpdeveloper1/api/critical-css-generator/pricing | https://rapidapi.com/ashishphpdeveloper1/api/critical-css-generator/pricing | https://rapidapi.com/ashishphpdeveloper1/api/critical-css-generator/pricing | https://rapidapi.com/ashishphpdeveloper1/api/critical-css-generator/pricing |
Key differences: Free is listed at 0 USD, Monthly Cost (crossed-out price on the card: 100 USD). Hobby is listed at 9 USD, Monthly Cost (crossed-out price on the card: 100 USD). Startup is listed at 29 USD, Monthly Cost (crossed-out price on the card: 100 USD). Business is listed at 99 USD, Monthly Cost (crossed-out price on the card: 100 USD). Items that are not listed on every plan: 50 Credits every Month (Free); Upto 1000 request every hour (Free); 1000 Credits every Month (Hobby); Upto 40 request every minute (Hobby); 6000 Credits every Month (Startup); Upto 60 request every minute (Startup); 15,000 Credits every Month (Business); Upto 120 request every minute (Business). A dash in the table means that line is not printed on that plan card. It is not an extra exclusion unless the card itself says “No”.
Start Free, Upgrade Anytime
Use it your way, test real features, build real things, and decide only when it truly fits your workflow.
Free
0 USD100 USDMonthly Cost
Services Include:
50 Credits every Month
Upto 1000 request every hour
Hobby
9 USD100 USDMonthly Cost
Services Include:
1000 Credits every Month
Upto 40 request every minute
Startup
29 USD100 USDMonthly Cost
Services Include:
6000 Credits every Month
Upto 60 request every minute
Business
99 USD100 USDMonthly Cost
Services Include:
15,000 Credits every Month
Upto 120 request every minute
Critical CSS API Cancellation and Refund Policy
How to cancel: Plans for this API are purchased through RapidAPI. To cancel, select Unsubscribe on the API plan page. You can cancel at any time.
When refunds apply: Under RapidAPI's terms, no refunds are issued when you cancel, including for any unused part of your subscription period.
Our refund policy: The W3SpeedUp refund policy applies to paid services sold on w3speedup.com. Read the full refund policy.
Frequently Asked Questions About the Critical CSS API
What does the Critical CSS API do?
The Critical CSS API automatically analyzes a webpage, identifies the styles required to render the above-the-fold content, and generates critical CSS. It eliminates the need to manually inspect stylesheets or identify essential CSS rules, helping developers optimize page rendering and improve website loading performance.
Which frameworks does the Critical CSS API support?
The Critical CSS API works with different web development frameworks and website types, including React, Vue, and static websites. Developers simply submit a webpage URL through the API and receive generated critical CSS that can be integrated into their projects.
Do I need to set up a headless browser to use the Critical CSS API?
No. The Critical CSS API handles webpage rendering and CSS analysis without requiring developers to configure or maintain their own headless browsers. It also eliminates the need to build and manage custom scripts for critical CSS generation.
Who is the Critical CSS API designed for?
The Critical CSS API is designed for theme and template developers, CMS and website builder platforms, website performance tool providers, and development teams. It is particularly useful for businesses that need to automatically generate critical CSS for multiple webpages during their build or deployment processes.
What pricing plans are available for the Critical CSS API?
The Critical CSS API offers four pricing plans. The Free plan includes 50 credits per month, Hobby costs $9 per month for 1,000 credits, Startup costs $29 per month for 6,000 credits, and Business costs $99 per month for 15,000 credits. API rate limits also increase with higher-tier plans, giving developers more capacity as their usage grows.
