Best SEO Keyword Suggestion APIs for Developers

Want to supercharge your app, tool, or website with keyword ideas? Keyword suggestion APIs give developers instant access to SEO-rich data without scraping or guessing.

Whether you're building a simple SEO tool, a WordPress plugin, or a marketing automation platform, these APIs can feed your software with smart keyword suggestions pulled from real search engines. Let’s explore how to use them, the best options out there, and how to plug them into your code like a pro.

Benefits of Using Keyword Suggestion APIs

So, why bother with a keyword API when there are dozens of tools out there?

Saves Time: No need to manually brainstorm keywords.
Automates SEO Tasks: Integrate into dashboards, plugins, or apps.
Live Data Access: Real-time suggestions as users type.
Custom UX: Build your own tool, style it your way.

Common Use Cases for Developers

Keyword suggestion APIs aren’t just for SEOs—they’re gold for developers too.

SEO Tools: Build your own keyword planner or analyzer.
CMS Plugins: Add real-time keyword ideas inside WordPress or Shopify.
Browser Extensions: Suggest keywords on SERP pages.
Dashboards: Feed marketing data into analytics panels.
Chatbots: Suggest content ideas dynamically.

Top Free and Paid Keyword Suggestion APIs

1. Google Ads Keyword Planner API (via Google Ads API)

Description: Official API by Google for fetching keyword ideas, search volume, competition, and CPC data.
Use Case: Industry-standard for keyword research.
Pricing: Free, but you must have a Google Ads account with active campaigns.
Documentation: https://developers.google.com/google-ads/api
Features:
- Keyword ideas from a seed keyword or URL
- Historical metrics (search volume, competition)
- Location targeting

2. DataForSEO API (Paid)

Description: Developer-friendly keyword research API offering extensive data like suggestions, SERP info, trends.
Use Case: SaaS apps, internal dashboards, keyword research tools.
Pricing: Pay-as-you-go or monthly packages.
Documentation: https://docs.dataforseo.com/
Features:
- Keyword suggestions
- CPC and volume by location/device
- SERP features and competition level

3. Keyword Tool API (keywordtool.io)

Description: Powerful keyword suggestion API based on autocomplete data from Google, YouTube, Amazon, Bing, etc.
Use Case: Multiplatform keyword discovery.
Pricing: Paid plans starting around $69/month.
Documentation: https://keywordtool.io/api
Features:
- Keyword ideas from autocomplete
- Long-tail keyword extraction
- Platform-specific keywords

4. Ubersuggest API (Neil Patel)

Description: Ubersuggest offers an unofficial or limited-use API for developers.
Use Case: Keyword research with SEO difficulty.
Pricing: Paid (plans starting at $29/month), limited access.
Docs: No official developer documentation, but accessible via backend APIs for personal use.
Features:
- Keyword suggestions
- SEO difficulty, CPC, and volume

5. SEO Review Tools API (Limited Free)

Description: Offers a handful of APIs including keyword suggestion.
Use Case: Embedding tools in websites, freelance projects.
Pricing: Free tier available, paid for higher limits.
Documentation: https://www.seoreviewtools.com/api/
Features:
- Keyword ideas and search volumes
- Long-tail and related keyword suggestions

6. Twinword Keyword Tool API (Freemium)

Description: AI-based keyword suggestion API that groups keywords by user intent.
Use Case: Intelligent keyword grouping for content marketers and tools.
Pricing: Free up to 500 requests/month, paid plans available.
Documentation: https://www.twinword.com/api/keyword-tool.php
Features:
- Related keywords
- Search volume, competition, and relevance
- Category and topic suggestions

7. SerpApi (Google Search Results API)

Description: Real-time Google search scraping API with keyword data.
Use Case: Extract keyword suggestions, People Also Ask, related searches.
Pricing: Paid (free trial available)
Documentation: https://serpapi.com/
Features:
- Get data from Google Autocomplete
- Access related and trending queries
- Scrape People Also Ask and more

8. Ahrefs API (Enterprise)

Description: High-end keyword and backlink data for enterprise SEO platforms.
Use Case: Advanced SEO tools and SaaS apps.
Pricing: Enterprise only.
Documentation: https://ahrefs.com/api
Features:
- Keyword metrics, click data, competition
- Historical keyword data
- Comprehensive SERP analysis

9. Moz Keyword Explorer API (Paid)

Description: Access Moz’s keyword research data.
Use Case: Integrate Moz metrics like Keyword Difficulty.
Pricing: Included in Moz Pro plans.
Documentation: https://moz.com/products/api
Features:
- Keyword suggestions
- SERP and difficulty score
- Volume and CTR metrics

10. H-supertools Keyword Suggestion API

Website: hsuper.tools
Pros: 100% free, fast JSON response
Data Includes: Keyword, volume, suggestions
Best For: Beginners, hobby projects, and small tools

Also Read:How to Embed SEO Tools on Website

What to Look for in a Keyword Suggestion API

Not all APIs are built equal. Before integrating one:

Speed: Latency matters for real-time use
Accuracy: Pulls from actual search engine trends
Data Depth: Volume, CPC, competition = value
Ease of Integration: Clean, well-documented APIs
Free Tier / Quotas: Know how much you can use

✅ Which API Should You Choose?

Use Case	Suggested API
Free + Reliable	Google Ads API (with Ads account)
Best Autocomplete Data	KeywordTool.io or Twinword
Advanced + Paid	DataForSEO or Ahrefs
Light Tools or Blogs	SEO Review Tools API or SerpApi
AI-Powered Keywords	Twinword API

How to Use a Keyword Suggestion API

API Authentication

Most APIs require an API key:

bash

GET https://api.example.com/keywords?query=seo

Headers: Authorization: Bearer YOUR_API_KEY

Making the First Request

Using fetch in JavaScript:

javascript

fetch('https://api.example.com/keywords?query=seo', {

headers: { 'Authorization': 'Bearer YOUR_API_KEY' }

})

.then(res => res.json())

.then(data => console.log(data));

Parsing the Response

You’ll get something like:

json

[

  {

    "keyword": "seo tips for beginners",

    "volume": 2900,

    "cpc": 1.5,

    "competition": 0.3

  }

]

You can loop through it and display suggestions on your UI.

Sample Code to Fetch Keyword Suggestions

JavaScript Example (Frontend)

javascript

async function getKeywords(query) {

  const res = await fetch(`https://api.hsuper.tools/keyword-suggestion?query=${query}`);

  const data = await res.json();

  console.log(data);

}

getKeywords("digital marketing");

Python Example

python

import requests

response = requests.get('https://api.hsuper.tools/keyword-suggestion?query=seo')

print(response.json())

PHP Example

php

$keyword = "seo";

$response = file_get_contents("https://api.hsuper.tools/keyword-suggestion?query=$keyword");

$data = json_decode($response, true);

print_r($data);

Building a Simple Keyword Suggestion Tool

Let’s make a basic tool using H-supertools’ free API.

Frontend:

html

<input type="text" id="keyword">

<button onclick="getKeywords()">Suggest</button>

<ul id="results"></ul>

<script>

  function getKeywords() {

    let q = document.getElementById("keyword").value;

    fetch(`https://api.hsuper.tools/keyword-suggestion?query=${q}`)

      .then(res => res.json())

      .then(data => {

        let list = data.map(k => `<li>${k.keyword} (Vol: ${k.volume})</li>`).join("");

        document.getElementById("results").innerHTML = list;

      });

  }

</script>

Tips for Scaling Your SEO Keyword Tool

Cache Results: Don’t hit the API repeatedly for same keyword
Paginate Suggestions: Show 10–20 at a time
Filter by Metrics: Let users filter by volume or difficulty
Combine APIs: Merge with Google Trends or SEMrush APIs

SEO Best Practices When Using APIs

Interpret the Data: Don’t just dump suggestions—add tips.
Focus on Intent: Categorize keywords (informational, commercial, etc.)
Create Pillar Pages: Use APIs to plan topic clusters.

Limitations of Free APIs

Let’s be honest—free has its limits:

Lower Rate Limits: Sometimes just 10–100 calls/day
Fewer Data Points: CPC, difficulty often missing
Slower Updates: Data may not be real-time

Also Read: Free SEO Tools for Digital Marketers

When to Upgrade to a Paid API

It’s worth going premium if:

You’re building a SaaS product
You need bulk keyword data
Your traffic is high and tools must respond instantly
You want accurate CPC for monetization strategies

Conclusion

If you're a developer aiming to create keyword research tools or SEO dashboards, a Keyword Suggestion API is your secret weapon. Free APIs like H-supertools are great to get started, while platforms like DataForSEO and Twinword offer advanced features as you scale.

Build, test, and deploy with confidence because keyword data is no longer locked behind big paywalls. You’ve got the keys. Time to create something epic.

FAQs

1. Is there a completely free SEO keyword API?
Yes, Hsupertools offers a free keyword suggestion API with zero cost and no login required.

2. Can I use Google’s API for keyword suggestions?
Not directly. Google Ads API requires approval and is focused on advertisers, not SEO. Use alternatives like Keyword Tool API.

3. How accurate are these keyword APIs?
Accuracy depends on the source. Premium APIs often mirror Google Ads data; free ones may offer estimates.

4. Are there open-source keyword APIs?
Some GitHub projects exist, but they usually scrape Google, which violates terms of service.5. Which API is best for a WordPress plugin?
Hsupertools or Twinword—both have developer-friendly JSON formats and allow integration without complex setup.