Understanding Client Hints: How Browsers Share Your Device Info

When studying browser fingerprints and device identification, Client Hints detection is always involved. As platform risk control continues to advance, the traditional UA-based identification is gradually becoming ineffective, and Client Hints perfectly fills this gap.

It not only affects the accuracy of browser fingerprint queries but also directly impacts website loading speed, precise ad targeting, and the reliability of risk control detection.

Next, we will explain in an easy-to-understand way the working principle of Client Hints, detection methods, use value, and future trends.

1. Why Did Client Hints Appear?

In the past, websites could only rely on the User-Agent sent by the browser to understand the visiting device. However, User-Agent carries too much information, which can be used to track users, conflicting with the recent emphasis on privacy.

Therefore, starting from Chromium-based browsers, User-Agent has been “lightened.” To avoid affecting websites’ ability to determine device characteristics, a more controllable, privacy-friendly, and on-demand mechanism called Client Hints was introduced.

In short: Client Hints = a mechanism for providing user device information on demand, where the platform says "I want it," and the browser decides "whether to provide it."

2. What Information Does Client Hints Transmit?

Client Hints does not expose all device information at once; its characteristic is "layered provision." These hint information can be roughly categorized as:

1. Default Information (Low Risk)

• Sec-CH-UA: Browser brand
• Sec-CH-UA-Mobile: Whether it is a mobile device
• Sec-CH-UA-Platform: Operating system platform

These generally do not involve sensitive privacy content.

2. Additional Information (High Precision)

For example, if a website wants to know the device CPU architecture, it needs to declare it via response headers:

The browser will return the corresponding information on the next request.

3. Client Hints Detection Principle: How the Browser Reports Data "On Demand"

Step 1: Server Declares Requirements

The server specifies the fields it wants in the response header:
Accept-CH: Sec-CH-UA-Full-Version, Sec-CH-UA-Model

Step 2: Browser Determines Whether to Allow Reporting

The browser decides whether to provide the data based on privacy policies. For example, some fields require HTTPS or long-term site access permission.

Step 3: Subsequent Requests Carry Client Hints Information

On the next visit to the same domain, the browser includes the corresponding headers to implement Client Hints detection.

This means: Client Hints is a "delayed effect" mechanism; declaring it does not immediately provide the data.

4. The Relationship Between Client Hints Detection and Browser Fingerprints

Many people worry: "Will Client Hints make fingerprint recognition easier?" The answer is not absolute.

Advantages: Data is more structured, reduces UA parsing complexity, and websites can only access the fields they declared.

Limitations: Many fields require HTTPS, some sensitive fields are not fully reported by browsers, and users can completely disable hints via browser settings.

Now Client Hints is often combined with other data (screen resolution, Canvas fingerprints, network conditions, etc.) to improve fingerprint stability.

5. Want to Debug Client Hints? Use the ToDetect Fingerprint Detection Tool

If you want to visually see which Client Hints your browser can report or test if a website’s configuration works, you can use the ToDetect Fingerprint Detection Tool:

• Displays traditional fingerprints and Client Hints return data simultaneously
• Detects whether the browser version has UA reduction applied
• Shows precise fields such as device platform, browser brand, and model
• Can be used to verify whether Accept-CH configuration is effective

For front-end developers, risk control engineers, and data security personnel, it is a very practical detection tool.

6. Future Trend: Will Client Hints Completely Replace UA?

Google has been promoting User-Agent Reduction (UA Reduction). In many future browser environments, User-Agent will only provide highly generalized information.

It can be anticipated that Client Hints will become one of the main methods for browser device identification. However, due to its privacy focus and limitations, using it for "strong fingerprints" is not realistic.

Summary

Client Hints detection is a mechanism designed by browsers to provide device information "on demand" for privacy purposes.

It complements or even replaces the traditional User-Agent. Using the ToDetect Fingerprint Detection Tool allows you to easily view the actual returned data.

For those studying browser device identification, optimizing page load, or conducting risk control testing, understanding Client Hints is a fundamental skill.