Open CaptchaWorld: A Comprehensive Web-based Platform for Testing and Benchmarking Multimodal LLM Agents

TL;DR

Open CaptchaWorld is a new web-based benchmark platform designed to evaluate multimodal large language models' visual reasoning and interaction skills through diverse CAPTCHA puzzles, revealing current models' limitations compared to humans.

Contribution

This paper introduces the first comprehensive platform and benchmark for testing multimodal LLM agents on interactive CAPTCHA tasks, including a novel metric for reasoning depth.

Findings

Humans achieve near-perfect CAPTCHA solving accuracy (93.3%).

State-of-the-art MLLM agents reach at most 40.0% success rate.

Open CaptchaWorld exposes significant gaps in current multimodal reasoning capabilities.

Abstract

CAPTCHAs have been a critical bottleneck for deploying web agents in real-world applications, often blocking them from completing end-to-end automation tasks. While modern multimodal LLM agents have demonstrated impressive performance in static perception tasks, their ability to handle interactive, multi-step reasoning challenges like CAPTCHAs is largely untested. To address this gap, we introduce Open CaptchaWorld, the first web-based benchmark and platform specifically designed to evaluate the visual reasoning and interaction capabilities of MLLM-powered agents through diverse and dynamic CAPTCHA puzzles. Our benchmark spans 20 modern CAPTCHA types, totaling 225 CAPTCHAs, annotated with a new metric we propose: CAPTCHA Reasoning Depth, which quantifies the number of cognitive and motor steps required to solve each puzzle. Experimental results show that humans consistently achieve near-perfect scores, state-of-the-art MLLM agents struggle significantly, with success rates at most 40.0% by Browser-Use Openai-o3, far below human-level performance, 93.3%. This highlights Open CaptchaWorld as a vital benchmark for diagnosing the limits of current multimodal agents and guiding the development of more robust multimodal reasoning systems. Code and Data are available at this https URL.