# Serpel, free: Related keywords API

> Starts from one seed keyword or topic. Combines keyword suggestions with related keywords, the seed first and then by search volume.

Serpel's Free plan for the related keywords API costs $0.00 per 1,000 keywords. Serpel's docs list all 6 fields on our checklist: Search volume, Monthly trend, Cost per click, Competition, Keyword difficulty, Search intent.
We haven't run Serpel through [our related keywords API benchmark](https://datacircle.dev/best-related-keywords-api.txt) yet.
This plan is free. We rank 226 plans for related keywords APIs by price. Half the plans cost $0.596 per 1,000 keywords or less. [See the best free related keywords API plan.](https://datacircle.dev/best-related-keywords-api.txt)
[Keys.so's ₽34,900 (about $417) monthly plan](https://datacircle.dev/related-keywords-apis/keys-so/34900-monthly/llms.txt) is the cheapest paid plan per 1,000 keywords. Keys.so's ₽34,900 (about $417) monthly plan charges nothing per call. You get as many keywords as Keys.so's rate limit allows.
[seodata.dev's $4.99 monthly plan](https://datacircle.dev/related-keywords-apis/seodata-dev/4-99-monthly/llms.txt) covers any number of keywords. seodata.dev's $4.99 monthly plan costs less up front than Keys.so's ₽34,900 (about $417) monthly plan.
[Bing Webmaster Tools](https://datacircle.dev/related-keywords-apis/bing-webmaster-tools/free/llms.txt), [DataForSEO](https://datacircle.dev/related-keywords-apis/dataforseo/top-up-from-50-pay-as-you-go-post-v3-dataforseo-labs-google-keyword-ideas-live/llms.txt) and [Mangools](https://datacircle.dev/related-keywords-apis/mangools/15-monthly/llms.txt) are the best related keywords API providers in the Datacircle benchmark.

- This page: https://datacircle.dev/related-keywords-apis/serpel/free
- [Related keywords API: the 9 best providers compared](https://datacircle.dev/best-related-keywords-api.txt)
- Get it: https://serpel.app/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- Request: `POST https://serpel.app/api/v1/keywords/research`
- API key: with the plan, on https://serpel.app/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- Its API docs: https://serpel.app/docs/keyword-research?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- Sold by: Serpel (https://serpel.app?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing)
- Checked: 2026-11-07

## In the answer

- Completeness: 100%
- Search volume: ✓
- Monthly trend: ✓
- Cost per click: ✓
- Competition: ✓
- Keyword difficulty: ✓
- Search intent: ✓

## Price

- $ per 1,000 keywords: $0.00
- Per: page of 50
- Billing: free

## Charges

- Start fee: $0.00
- Also pays for: from the same budget: Rank check right now · ChatGPT answer check · Google AI Overview check · Keyword research for a domain · List research · Site crawl · Monitoring run

## Overage

- Units cap: hard

## Not found

- $ per 1,000: $0.00

## In their words

- Their pitch: Starts from one seed keyword or topic. Combines keyword suggestions with related keywords, the seed first and then by search volume.

## Data

- Freshness: 7 days
- Keep data: no limit
- Use data: § 11 (1) "[...] the non-exclusive, non-transferable right to use Serpel within the scope of these terms." (2) "You use Serpel lawfully only. You do not bypass technical limits such as rate limits or plan limits, you do not put excessive load on the systems and you do not pass on your login details. [...]" (3) "You may have only websites checked and crawled that you own or are authorised to check, for example websites of clients that you look after. [...]" (4) "[...] Do not enter data that you are not authorised to use. [...]"

## Plan

- Pay: €0
- You get: 100 credits
- Enough for: 25 pages, once
- Expires: never

## Rate limit

- Per second: 0.5
- Batch: 1

## Speed

- Answer: in the call

## The call

- You send: mode "keyword", keyword. Optional: country, language, limit, Idempotency-Key header
- Method: POST
- Path: /keywords/research

## About the plan

- Plan: Free
- Who can get it: anyone aged 18 or older with full legal capacity, as a consumer or a business

## The 10 fields the plan's answer can hold

keyword, location code, language code, search volume, monthly searches, cost per click, keyword difficulty, main intent, competition, competition level

## Serpel's plans (7)

- [Serpel, free](https://datacircle.dev/related-keywords-apis/serpel/free/llms.txt): $0.00 per 1,000, 100% complete, 7 days
- [Serpel, €5 pack](https://datacircle.dev/related-keywords-apis/serpel/5-pack/llms.txt): $0.90 per 1,000, 100% complete, 7 days
- [Serpel, €10 pack](https://datacircle.dev/related-keywords-apis/serpel/10-pack/llms.txt): $0.90 per 1,000, 100% complete, 7 days
- [Serpel, €25 pack](https://datacircle.dev/related-keywords-apis/serpel/25-pack/llms.txt): $0.90 per 1,000, 100% complete, 7 days
- [Serpel, €50 pack](https://datacircle.dev/related-keywords-apis/serpel/50-pack/llms.txt): $0.90 per 1,000, 100% complete, 7 days
- [Serpel, €19 monthly](https://datacircle.dev/related-keywords-apis/serpel/19-monthly/llms.txt): $0.855 per 1,000, 100% complete, 7 days
- [Serpel, €49 monthly](https://datacircle.dev/related-keywords-apis/serpel/49-monthly/llms.txt): $0.735 per 1,000, 100% complete, 7 days

## Serpel's calls for this API (1)

- `POST /keywords/research`: [Serpel, free](https://datacircle.dev/related-keywords-apis/serpel/free/llms.txt)

## Serpel's APIs (5)

- [Serpel: ChatGPT scraper API pricing, 7 plans](https://datacircle.dev/chatgpt-scraper-apis/serpel/free/llms.txt)
- [Serpel: ranked keywords API pricing, 7 plans](https://datacircle.dev/ranked-keywords-apis/serpel/free/llms.txt)
- [Serpel: related keywords API pricing, 7 plans](https://datacircle.dev/related-keywords-apis/serpel/free/llms.txt)
- [Serpel: Google AI Overview scraper API pricing, 7 plans](https://datacircle.dev/google-ai-overview-scraper-apis/serpel/free/llms.txt)
- [Serpel: SERP API pricing, 7 plans](https://datacircle.dev/serp-apis/serpel/free/llms.txt)

## Serpel: related keywords API alternatives

- [DataForSEO, top-up from $50, Pay as you go, POST /v3/keywords_data/bing/keywords_for_keywords/live](https://datacircle.dev/related-keywords-apis/dataforseo/top-up-from-50-pay-as-you-go-post-v3-keywords-data-bing-keywords-for-keywords-live/llms.txt): $0.03 per 1,000, 67% complete, live
- [OpenRush, top-up from $10](https://datacircle.dev/related-keywords-apis/openrush/top-up-from-10/llms.txt): $0.15 per 1,000, 17% complete, 1 day
- [QuanticData, $79 monthly](https://datacircle.dev/related-keywords-apis/quanticdata/79-monthly/llms.txt): $0.253 per 1,000, 0% complete, live
- [OutlierKit, $1,999 yearly](https://datacircle.dev/related-keywords-apis/outlierkit/1999-yearly/llms.txt): $0.833 per 1,000, 33% complete, live

## Sources

From each provider's own pricing page and docs, and from what providers tell us. We read this row from these pages on 2026-11-07.

- https://serpel.app/docs/api?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- https://serpel.app/docs/credits-and-billing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- https://serpel.app/docs/keyword-research?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- https://serpel.app/llms.txt?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- https://serpel.app/pricing?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing
- https://serpel.app/terms?utm_source=datacircle.dev&utm_medium=referral&utm_campaign=related-keywords-api-pricing