Underpage: Web DevTools

See what's under any web page. Underpage is a browser with Chrome-style developer tools built in: network, elements, console, storage, performance, security and Lighthouse audits, on your Android phone or tablet.

WHY UNDERPAGE
• Inspect real pages on a real phone, exactly as your mobile users see them.
• Seven DevTools panels in one app: Network, Elements, Console, Application, Performance, Security and Lighthouse.
• Lighthouse audits with the same scores as Chrome, and a progress bar that shows the time left.
• Request rules and breakpoints: mock, redirect, block, delay or edit any request.
• No root, no VPN, no computer, no account. Smooth even on heavy, ad-filled sites.

NETWORK
• Every request live: status, method, type, size, time, priority, initiator and protocol (HTTP/1.1, HTTP/2, HTTP/3).
• Headers, cookies, query strings, timing waterfall and certificate for each request.
• Response viewers for JSON, code, images, SVG, fonts and media; code is formatted and highlighted, with folding, search and full screen.
• Filter by type, search, preserve log, group by frame, pick and pin columns.
• Throttle to Slow 3G, Slow 4G, Fast 4G or offline; disable the cache.
• WebSocket and Server-Sent Event messages live.
• GraphQL queries, mutations, subscriptions and batches detected automatically.
• Image gallery: every image a page loaded, animated and SVG too, ready to save.

ELEMENTS
• Live DOM tree with Styles, Computed, Layout and Accessibility.
• Tap Inspect, then anything on the page, to select it with its box model drawn.
• Edit attributes, text, HTML and styles; copy a selector, XPath or outerHTML.

CONSOLE
• Logs, errors with stack traces, warnings and violations, each with its source.
• A JavaScript prompt with autocomplete, history, live expressions and eager results.
• Expandable objects, console.table, $0, $$, copy() and inspect().
• debug() pauses with call stack and scopes; profile() records a CPU profile you can save.

LIGHTHOUSE
• Chrome DevTools' own Lighthouse 13: Performance, Accessibility, Best practices and SEO.
• Navigation, Timespan and Snapshot modes, mobile or desktop.
• Accurate progress with time left; the page is locked while it runs, so results stay clean.
• Scores, metrics and every audit with tappable "Learn more" links, plus the full report with treemap. Save it as HTML or JSON.

PERFORMANCE
• Record, or reload and record: flame chart, screenshots, Summary, Bottom-up, Call tree and Event log.
• CPU throttling; live monitor for CPU, JS heap, DOM nodes and layouts.

APPLICATION
• Browse and edit local and session storage, cookies, IndexedDB, Cache Storage, shared storage and storage buckets.
• Manifest, service workers, storage quota and clear site data.
• Back/forward cache, background services, Reporting API, speculative loads, bounce tracking, interest groups and private state tokens.
• Frames: security and isolation, permissions policy and every resource the frame loaded.

SECURITY
• HTTPS and certificate details for the page and every origin it loads, with mixed-content warnings.

REQUEST RULES
• Redirect, mock a response, block or delay requests by URL.
• Add, change or remove headers; rewrite query strings and bodies.
• Breakpoints pause a request or response so you can edit it before it continues.
• See which rules changed each request, and export your rules.

A REAL BROWSER
• Tabs with previews, private tabs, desktop site and a pop-up blocker.
• Resizable DevTools area, dark and light themes, built for touch.

PRIVACY
The pages you browse, the traffic you capture and your rules stay on your device. Underpage sends crash reports and anonymous feature-usage statistics, which you can turn off in Settings. Privacy policy: https://underpage-app.web.app/privacy

Underpage is independent and not affiliated with Google or any browser maker. Lighthouse belongs to its respective owner.