Choose the appropriate reCAPTCHA key type

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reCAPTCHA keys (also known as keys), let you protect your endpoints by verifying user interactions on your web pages and mobile applications.

To choose the appropriate reCAPTCHA key type, you must understand the types of keys that are supported for each platform and their differences.

Types of reCAPTCHA keys

The following table lists reCAPTCHA keys that are supported for each platform:

Platform	Description	Supported keys	Challenge type
web	For integration on web pages.	Score-based keys	SCORE
		Checkbox keys	CHECKBOX
mobile	For integration with Android and iOS apps.	reCAPTCHA keys for Android	SCORE
		reCAPTCHA keys for iOS	SCORE
WAF	For web pages and APIs served through WAF or Edge compute servers.	action-token keys	SCORE and CHECKBOX
		session-token keys	SCORE
		challenge-page keys	INVISIBLE
API	For integration with APIs or clients like IoT devices that do not support the reCAPTCHA JavaScript or mobile SDKs.	express keys	SCORE

Choose a reCAPTCHA key type for web

For websites, reCAPTCHA provides score-based (no challenge) and checkbox (checkbox visual challenge) keys to verify user interactions. Both key types return a score for each request, which is based on interactions with your site. This score lets you understand the level of risk that the interaction poses and helps you to take appropriate actions for your site.

The following table summarizes the differences between score-based and checkbox keys, and helps you choose the appropriate key based on your use cases:

Comparison category	Score-based key (Recommended)	Checkbox key
Description	Score-based keys let you verify whether an interaction is legitimate without any user interaction.	Checkbox keys use a checkbox challenge that requires user interaction to verify that the user is not a robot. Also, you can use checkbox keys to protect specific actions with CAPTCHA challenges.
How it works	With score-based keys, the reCAPTCHA Enterprise API returns a score, which you can use to take action in the context of your site. Examples of actions you might take include requiring additional factors of authentication, sending a post to moderation, or throttling bots that might be scraping content.	A checkbox key renders an I'm not a robot checkbox that a user must click to verify that they're not a robot. This checkbox key might or might not challenge them with CAPTCHA challenges. In both cases, the reCAPTCHA Enterprise API returns a score. CAPTCHA challenges require a user to select certain kinds of objects, such as street signs, from a collection of images. The following animated GIF is an example of a checkbox key: The following image shows a sample CAPTCHA challenge: Before using CAPTCHA challenges, you must understand the CAPTCHA challenges caveats.
Supported platforms	Websites and mobile platforms.	Websites only.
Use cases	Score-based keys are appropriate for the following use cases: Websites that have accessibility requirements. For payment-related transactions that prefer less friction for better conversion rates. Situations where you want to use additional features such as password check (Password defense) or Multi-factor authentication (MFA). Sites accessed through mobile applications.	Checkbox keys are appropriate for forms, logins, and signups on web pages. Though it might cause extra friction for users, an extra step such as CAPTCHA challenge helps to deter unsophisticated attackers.

Caveats with CAPTCHA challenges

If you want to use checkbox keys with CAPTCHA challenges to protect against automated attacks, be aware of the following caveats:

• CAPTCHAs require user interaction, which increases friction and might decrease conversion rates.
• Due to the advances in computer vision and machine intelligence, CAPTCHAs are becoming less useful to distinguish between humans and bots.
• CAPTCHAs are also under threat from paid attackers who can solve all types of challenges.
• CAPTCHAs are not accessible for all users, so they might not be suitable if your website has accessibility requirements.

Choose reCAPTCHA key types for WAF

reCAPTCHA for WAF integrations support action-tokens, session-tokens, challenge page, and reCAPTCHA express

You can use one or more features of reCAPTCHA for WAF in a single application. For example, you can choose to apply a session-token for all pages, and based on the session-token's score, you can redirect suspicious requests to the reCAPTCHA challenge page. Also, you can use an action-token for high-profile actions, such as checkout. For more information, see examples.

The following table shows a brief comparison of the available reCAPTCHA for WAF features:

Comparison category	reCAPTCHA action-tokens	reCAPTCHA session-tokens	reCAPTCHA challenge page	reCAPTCHA express
Use case	Use to protect user actions, such as login or comment posts.	Use to protect the whole user session on the site's domain.	Use when you suspect spam activity directed to your site and you need to screen out bots. This method interrupts a user's activity because the user has to verify a CAPTCHA challenge.	Use reCAPTCHA express when your environment does not support the integration of the reCAPTCHA JavaScript or the mobile SDKs.
Supported platforms	Websites and mobile applications	Websites	Websites	All HTTP Requests. Including: APIs, websites, mobile applications, and IoT devices such as TVs and gaming consoles
Client integration effort	Medium Manual client-side integration.	Medium Install reCAPTCHA JavaScript manually or through injection on the WAF.	Low Interstitial triggered by security policies.	Low No client integration.
Detection accuracy	Highest Client, server, and action specific signals are available.	High Client and server speicific signals are available.	Medium Client and server speicific signals are available. Client signals are only available in an interstitial page.	Low Only server-side signals are available.
Supported reCAPTCHA version	reCAPTCHA score-based and checkbox keys	reCAPTCHA score-based keys	reCAPTCHA challenge-based keys embedded in an interstitial page	reCAPTCHA express keys

Choose reCAPTCHA express keys for APIs

Use reCAPTCHA express when your environment does not support a reCAPTCHA client integration like the JavaScript API or the mobile SDKs. reCAPTCHA express is suitable for APIs, websites, mobile applications, and IoT devices such as TVs and gaming consoles, but can also be used to protect websites or mobile applications when a client-side integration is infeasible.

Because reCAPTCHA express is a server-side only integration, it lacks client-side signal collection. This typically results in a lower detection accuracy than integrations that involve a client-side component.

What's next

• Create reCAPTCHA keys for websites.
• Create reCAPTCHA keys for mobile applications.
• Learn more about reCAPTCHA keys for WAF.
• Learn more about reCAPTCHA express keys for APIs.