Dev shares 5 hard lessons from building a Chrome extension for AI chat platforms

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A developer spent several months building a Chrome extension called HTML Deployer, which detects and deploys HTML code blocks generated by ChatGPT, Claude, and Gemini to live URLs. The builder found that monitoring three constantly-updated chat interfaces was far harder than the deployment logic itself, requiring debounced MutationObservers and structural DOM pattern matching instead of fragile class-name selectors. Scoring candidate HTML blocks by content quality — rather than grabbing the first match — significantly reduced false positives during extraction. Security concerns also shaped the design: iframes are sandboxed explicitly, and user credentials are never routed through the developer's own backend. Unexpectedly, user trust around credential handling proved to be the most impactful issue to address clearly in documentation after launch.

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