Best alternatives to hwatu in 2026

A coding agent that changes CSS or a component's layout has no real way to know whether the change looks right — it can read the code it wrote, but it can't see the rendered result the way a human reviewer would. hwatu closes that gap: it's a background WebKitGTK daemon that keeps a browser view prewarmed and ready (already loaded, GPU compositor hot), so opening a fresh window takes a median of 13ms instead of the usual multi-second browser startup. Once open, it doesn't just take a screenshot — it produces pixel-difference scoring with heatmaps, and quantifies animations as concrete metrics (duration, easing, velocity) rather than a subjective "looks smooth" judgment. It connects to agents via an MCP server, ships with a built-in ad blocker using 119k EasyList rules, and — because it's genuinely a working browser, not just a screenshot tool — doubles as a fast daily browser for people using tiling window managers.