# How to choose a gender inference API

> Compare GenderAPI.io, Genderize, Gender-API.com, Namsor and NameGender by inputs, confidence, unknown handling, batch workflows and credit accounting.

Canonical HTML: https://www.genderapi.io/how-to-choose-a-gender-inference-api

Last reviewed: 2026-09-26

## About this comparison

Published by GenderAPI.io, one of the providers discussed. This is a dated review of public documentation, not an independent performance test or an endorsement by another provider. We did not run competitor prediction requests. Undocumented in a reviewed reference does not mean unavailable. Recheck the linked contract and pricing before integrating.

## Start with the data you actually have

Choose a provider around your input format, required evidence and operational constraints. A name-only lookup, email-name extraction and nickname inference are different tasks. A familiar confidence field or a large database does not establish accuracy on your records.

| Provider | Documented starting point | Detailed comparison | Sources |
| --- | --- | --- | --- |
| GenderAPI.io V2 | Unified name, email and username requests; explicit dataset/AI options. | Current V2 documentation | [GenderAPI.io V2 request parameters](https://www.genderapi.io/docs/v2/request-parameters); [GenderAPI.io V2 AI options](https://www.genderapi.io/docs/v2/ai-options) |
| Genderize.io | Name or full-name GET lookups with optional country context. | Name-focused interface and migration checks | [Gender API reference](https://genderize.io/documentation/api/reference) |
| Gender-API.com | V2 name/full-name/email requests, including name extraction fields. | Separate service, contract and unknown billing | [Gender-API.com v2: Query by full name](https://gender-api.com/en/api-docs/v2/query-by-full-name); [Gender-API.com v2: Query by email address](https://gender-api.com/en/api-docs/v2/query-by-email-address) |
| Namsor | Structured or full-name gender routes, with country-aware variants. | Name inputs, score meanings and batch mapping | [Namsor Gender API: Predict gender from first or full names](https://namsor.app/api-documentation/gender-api/) |
| NameGender.com | Separate name/email/username routes with optional AI fallback. | AI defaults, score scales and batch structure | [REST API Reference — NameGender](https://namegender.com/docs) |

- [GenderAPI.io V2 documentation](https://www.genderapi.io/api-documentation)
- [GenderAPI.io vs Genderize.io](https://www.genderapi.io/genderapi-io-vs-genderize-io)
- [GenderAPI.io vs Gender-API.com](https://www.genderapi.io/genderapi-io-vs-gender-api-com)
- [GenderAPI.io vs Namsor](https://www.genderapi.io/genderapi-io-vs-namsor)
- [GenderAPI.io vs NameGender.com](https://www.genderapi.io/genderapi-io-vs-namegender-com)

## Use a checklist before comparing prices

These are selection questions, not universal promises about every provider. The linked comparisons identify which behavior is documented for each service. Review security, retention and contractual requirements directly with the provider when those affect your decision.

| Question | What to check | Sources |
| --- | --- | --- |
| Can it process the input I have? | Test first names, full names, scripts, aliases and missing values separately. Country context must be known, not guessed from a person’s name. | [GenderAPI.io V2 request parameters](https://www.genderapi.io/docs/v2/request-parameters) |
| What does an answer mean? | Separate an inferred gender association from identity. Inspect unknown behavior, evidence counts and score definitions. Do not carry a threshold between providers untested. | [GenderAPI.io V2 responses](https://www.genderapi.io/docs/v2/responses); [GenderAPI.io accuracy methodology](https://www.genderapi.io/accuracy-methodology) |
| What happens in a batch? | Check item limits, input types, per-item country, preserved IDs, partial errors and the account quota. One HTTP request may consume many credits. | [GenderAPI.io V2 batch guide](https://www.genderapi.io/docs/v2/batch) |
| When is AI involved? | Choose an explicit policy; defaults and opt-in controls differ. Review what input reaches an inference service and the published processing terms. | [GenderAPI.io V2 AI options](https://www.genderapi.io/docs/v2/ai-options) |
| What will the job cost? | Count ordinary, AI and unknown operations; include retries and overages. Compare the same workload and payment period, then consult current prices. | [GenderAPI.io V2 credits and usage](https://www.genderapi.io/docs/v2/credits-and-usage); [GenderAPI.io pricing](https://www.genderapi.io/price) |

## Estimate workload cost before buying a plan

Illustrative GenderAPI.io V2 calculation: 1,000 successful ordinary lookups cost 1,000 credits, including unknowns and ordinary fallback AI. If all 1,000 use forceToGenderize and 200 require AI, the cost is 800 × 1 + 200 × 2 = 1,200 credits. These invented proportions are not measured match rates.

Apply each other provider’s own charging rules to the same workload; do not equate a name, HTTP request, answered result and AI operation. Retries can add usage. This review does not calculate a cheapest-provider ranking.

Sources: [GenderAPI.io V2 credits and usage](https://www.genderapi.io/docs/v2/credits-and-usage)

- [GenderAPI.io credit rules](https://www.genderapi.io/docs/v2/credits-and-usage)
- [Current GenderAPI.io plans](https://www.genderapi.io/price)

## Evaluate the workflow you will deploy

Choose a representative sample you are permitted to process and keep the original inputs, preprocessing and country context fixed. Evaluate name, email and username workflows separately. Record provider, endpoint, date, configuration and whether AI was used.

Measure coverage (answered / eligible), accuracy among answered results (correct / answered), and correct results across all eligible inputs (correct / eligible). Report unknowns, errors, costs and latency separately. A threshold should be selected on validation data and then checked on a held-out sample.

GenderAPI.io does not publish an independent reference-labelled accuracy benchmark here. Database counts, contract tests and one provider's published study cannot establish which service will work best on your data. An inferred association does not establish a person's gender identity.

Sources: [GenderAPI.io accuracy methodology](https://www.genderapi.io/accuracy-methodology)

- [Our methodology and current evidence limits](https://www.genderapi.io/accuracy-methodology)
- [Dated database profile](https://www.genderapi.io/data-provenance)

## Which gender API is the most accurate?

This documentation review cannot establish a winner. Compare providers on the same permitted, reference-labelled sample, report coverage and errors as well as accuracy, and keep country and AI settings explicit.

Sources: [GenderAPI.io accuracy methodology](https://www.genderapi.io/accuracy-methodology)

## Can I compare all confidence scores directly?

No. Scores can differ in units, calibration and evidence. Some fields are categories, some are probabilities and some are unnormalized scores. A numeric conversion alone does not make them comparable.

Sources: [GenderAPI.io accuracy methodology](https://www.genderapi.io/accuracy-methodology); [NameGender API OpenAPI 3.1 contract, info.version 1.0.0](https://namegender.com/openapi.json); [Namsor Gender API: Predict gender from first or full names](https://namsor.app/api-documentation/gender-api/)

## Can I treat an inferred result as a person’s identity?

No. Name-related inference is an association. Keep unknown outcomes and let information supplied by the person take precedence.

Sources: [GenderAPI.io accuracy methodology](https://www.genderapi.io/accuracy-methodology)

## Sources and review date

- [GenderAPI.io V2 request parameters](https://www.genderapi.io/docs/v2/request-parameters): Reviewed 2026-09-26
- [GenderAPI.io V2 authentication](https://www.genderapi.io/docs/v2/authentication): Reviewed 2026-09-26
- [GenderAPI.io V2 responses](https://www.genderapi.io/docs/v2/responses): Reviewed 2026-09-26
- [GenderAPI.io V2 AI options](https://www.genderapi.io/docs/v2/ai-options): Reviewed 2026-09-26
- [GenderAPI.io V2 batch guide](https://www.genderapi.io/docs/v2/batch): Reviewed 2026-09-26
- [GenderAPI.io V2 credits and usage](https://www.genderapi.io/docs/v2/credits-and-usage): Reviewed 2026-09-26
- [GenderAPI.io accuracy methodology](https://www.genderapi.io/accuracy-methodology): Reviewed 2026-09-26
- [GenderAPI.io pricing](https://www.genderapi.io/price): Reviewed 2026-09-26
- [Gender-API.com v2: Query by email address](https://gender-api.com/en/api-docs/v2/query-by-email-address): Reviewed 2026-09-26
- [Gender-API.com v2: Query by full name](https://gender-api.com/en/api-docs/v2/query-by-full-name): Reviewed 2026-09-26
- [Gender API reference](https://genderize.io/documentation/api/reference): Reviewed 2026-09-26
- [NameGender API OpenAPI 3.1 contract, info.version 1.0.0](https://namegender.com/openapi.json): Reviewed 2026-09-26
- [REST API Reference — NameGender](https://namegender.com/docs): Reviewed 2026-09-26
- [Namsor Gender API: Predict gender from first or full names](https://namsor.app/api-documentation/gender-api/): Reviewed 2026-09-26