Artificial Intelligence

Reduce CAPTCHAs for AI agents browsing the web with Web Bot Auth (Preview) in Amazon Bedrock AgentCore Browser

AI agents need to browse the web on your behalf. When your agent visits a website to gather information, complete a form, or verify data, it encounters the same defenses designed to stop unwanted bots: CAPTCHAs, rate limits, and outright blocks.

Today, we are excited to share that AWS has a solution. Amazon Bedrock AgentCore Browser, our secure, cloud-based browser for AI agents to interact with websites, now supports Web Bot Auth (in preview), a draft IETF protocol that gives agents verifiable cryptographic identities.

CAPTCHA friction

Customers tell us that CAPTCHA friction is one of the biggest obstacles to reliable browser-based agentic workflows. Your agent halts mid-task, waiting for human intervention to solve a puzzle that proves you’re not a bot – except your agent is a bot, and that’s the point. CAPTCHAs exist for good reason. Websites face constant challenges protecting their content, inventory and reviews. Web Application Firewalls (WAFs) and bot detection services protect these sites, but they treat nearly all automated traffic as suspicious because they have no reliable way to distinguish legitimate agents from malicious ones.

Some automation providers try to solve CAPTCHAs programmatically – using computer vision models to read distorted text or clicking through image grids until the puzzle clears. This approach is brittle, expensive, and is bypassing controls that domain owners intended for their content. Other approaches rely on IP allowlists or User-Agent strings. IP allowlists break when you run agents in cloud environments where addresses change frequently. User-Agent strings can be spoofed by anyone, so they provide no verification, and pose a risk of people emulating well trusted strings. Both methods require manual coordination with every website you want to access, which does not scale.

Web Bot Auth: Cryptographic identity for agents browsing the web

Web Bot Auth is a draft IETF protocol that gives agents verifiable cryptographic identities. When you enable Web Bot Auth in AgentCore Browser, we issue cryptographic credentials that websites can verify. The agent presents these credentials with every request. The WAF may now additionally check the signature, confirm it matches a trusted directory, and allow the request through if verified bots are allowed by the domain owner and other WAF checks are clear.

AgentCore is working with Cloudflare, HUMAN Security, and Akamai Technologies to support this verification flow. These providers protect millions of websites. When you create an AgentCore Browser with signing enabled in the configuration, we automatically register your agent’s signature directory with these providers. Many domains already configure their WAFs to allow verified bots by default, which means you can see immediate CAPTCHA reduction without additional setup in the cases that this happens.

How domain owners control access

WAF providers give website owners three levels of control using Web Bot Auth:

  • Block all bots – Some sites choose to block automated traffic entirely. Web Bot Auth does not bypass this – if a domain wants no automation, that choice is respected.
  • Allow verified bots – Many domains configure their WAF to allow any bot that presents a valid cryptographic signature. This is the default policy for a growing number of sites protected by Cloudflare, HUMAN Security, and Akamai Technologies. When you enable signing, as a parameter in the AgentCore Browser configuration, this policy will apply to your agents.
  • Allow specific verified bots to conduct only specific actions – For example, a financial services company automating vendor portal access can share its unique directory with those vendors. The vendor can create rules like “allow FinCo agents at 100 requests per minute, don’t allow them to create new accounts, and block all other signed agents.” This gives websites granular control while preserving the benefits of cryptographic verification.

Today’s preview release of Web Both Auth support in AgentCore Browser helps reduce friction with CAPTCHAs on domains that allow verified bots, by making your agent appear as a verified bot. Once the Web Bot Auth protocol is finalized, AgentCore intends to transition to customer-specific keys, so AgentCore users can use the tier of control that allows only specified verified bots.

Using the Web Bot Auth protocol

To enable the browser to sign requests using the Web Bot Auth protocol, create a browser tool with the browserSigning configuration:

import boto3
cp_client = boto3.client('bedrock-agentcore-control')
response = cp_client.create_browser(
    name="signed_browser",
    description="Browser tool with Web Bot Auth enabled",
    networkConfiguration={
        "networkMode": "PUBLIC"
    },
    executionRoleArn="arn:aws:iam::123456789012:role/AgentCoreExecutionRole",
    browserSigning={
        "enabled": True
    }
)
browserId = response['browserId']

Pass the browser identifier to your agent framework. Here is an example using Strands Agents:

from strands import Agent
from strands_tools.browser import AgentCoreBrowser
agent_core_browser = AgentCoreBrowser(
    region="us-west-2",
    identifier=browserId
)
strands_agent = Agent(
    tools=[agent_core_browser.browser],
    model="anthropic.claude-4-5-haiku-20251001-v1:0",
    system_prompt="You are a website analyst. Use the browser tool efficiently."
)
result = strands_agent("Analyze the website at <https://example.com/>")

The agent is now configured to use the new browser tool that signs every HTTP request. Websites protected by Cloudflare, HUMAN Security, or Akamai Technologies can verify the signature and allow the request through without presenting a CAPTCHA, if the domain owner allows verified bots.

Protocol development

The Web Bot Auth protocol is gaining industry momentum because it solves a real problem: legitimate automation is indistinguishable from abuse without verifiable identity. You can read the draft protocol specification, HTTP Message Signatures for automated traffic Architecture. The architecture defines how agents generate signatures, how WAFs verify them, and how key directories enable discovery. Amazon is working with Cloudflare and many popular WAF providers to help finalize the customer-specific key directory format and work towards finalizing the draft.

Conclusion

Amazon Bedrock AgentCore Browser is generally available, with the Web Bot Auth feature available in preview. AgentCore Browser signing requests using the Web Bot Auth protocol help reduce friction with CAPTCHA across domains that allow verified bots. As the protocol finalizes, AgentCore Browser intends to issue customer-specific keys and directories, so you can prove your agent’s identity to specific websites and establish trust relationships directly with the domains you need to access.

Web Bot Auth enables agents to prove their identity when challenged, reduces operational friction in automated workflows, and gives website owners control over which agents access their resources. Amazon Bedrock AgentCore Browser support for Web Bot Auth (Preview) provides the infrastructure layer that makes this possible. Try out AgentCore Browser in your account, with our samples on Github.

About the authors

Veda Raman is a Senior Specialist Solutions Architect for generative AI and machine learning at AWS. Veda works with customers to help them architect efficient, secure, and scalable machine learning applications. Veda specializes in generative AI services like Amazon Bedrock and Amazon SageMaker.

Kosti Vasilakakis is a Principal PM at AWS on the Agentic AI team, where he has led the design and development of several Bedrock AgentCore services from the ground up, including Runtime, Browser, Code Interpreter, and Identity. He previously worked on Amazon SageMaker since its early days, launching AI/ML capabilities now used by thousands of companies worldwide. Earlier in his career, Kosti was a data scientist. Outside of work, he builds personal productivity automations, plays tennis, and enjoys life with his wife and kids.

Joshua Samuel is a Senior AI/ML Specialist Solutions Architect at AWS who accelerates enterprise transformation through AI/ML, and generative AI solutions, based in Melbourne, Australia. A passionate disrupter, he specializes in agentic AI and coding techniques – Anything that makes builders faster and happier.