The web viewer module in OpenROAD (web) provides a browser-based interface for exploring chip layouts and performing design analysis. It renders the design as PNG tiles served over WebSocket, enabling smooth zoom and pan of large designs without a native GUI.

- Parameters in square brackets `[-param param]` are optional.
- Parameters without square brackets `-param2 param2` are required.

Start the web viewer server. This opens a WebSocket server and launches the viewer in the default browser.

web_server
    [-port port]
    -dir dir

Save the layout to a PNG file. By default, the command uses the GUI (Qt) renderer. Pass -web to use the web tile renderer instead, which runs entirely server-side without a display and is suitable for headless CI.

save_image
    [-web]
    [-area {x0 y0 x1 y1}]
    [-width width]
    [-resolution microns_per_pixel]
    [-display_option option]
    path

When using -web, if neither -width nor -resolution is specified, the image defaults to 1024 pixels wide. The maximum image dimension is 16384 pixels; larger requests are clamped automatically.

Display options control which elements are rendered when using -web. Each option is a {key value} pair where the key matches a visibility field and the value is true or false.

# Save using the GUI renderer (default)
save_image layout.png

# Save using the web renderer (headless)
save_image -web layout.png

# Save at 1024px wide with the web renderer
save_image -web -width 1024 layout.png

# Save at 0.1 um per pixel
save_image -web -resolution 0.1 layout.png

# Save a specific region (in microns)
save_image -web -area {0 0 100 100} -width 2048 region.png

# Hide routing and power nets
save_image -web -display_option {routing false} \
                -display_option {net_power false} \
                layout.png

Generate a self-contained HTML timing report. The report uses the same JavaScript frontend as the live web viewer but serves all data from a cache embedded in the HTML file. No running server is required to view the report.

web_save_report
    [-setup_paths count]
    [-hold_paths count]
    path

The report includes:

• Layout view with pre-rendered tiles at a fixed zoom level. Layer visibility can be toggled using the same display controls as the live viewer. Zoom is disabled; pan is allowed.
• Timing table with setup and hold paths. Clicking a path highlights it on the layout via a pre-rendered overlay image.
• Slack histogram with setup/hold tabs.
• Display controls, hierarchy browser, clock tree, and other panels from the live viewer (features that require server interaction show empty states).

The report requires an internet connection to load Leaflet and GoldenLayout CSS/JS from CDN.

# Generate a report with default settings
web_save_report timing.html

# Include more paths
web_save_report -setup_paths 200 -hold_paths 200 timing.html

• Tile-based rendering — The server renders 256x256 PNG tiles on demand, supporting smooth zoom and pan of designs with millions of instances.
• Object inspection — Click on instances, nets, pins, or other objects to view their properties in an inspector panel. Hover highlights are rendered server-side in tiles.
• Timing analysis — View timing paths with slack, delay, and arrival time metrics. Highlight critical paths on the layout. Slack histogram charts with filtering by path group and clock domain.
• Clock tree visualization — Browse clock tree hierarchy, highlight clock paths, and view per-level statistics.
• Hierarchy browser — Navigate the module tree with instance counts and area statistics. Toggle visibility and assign colors per module using a 31-color palette.
• Display controls — Toggle visibility of cell types (stdcells, macros, pads), net types (signal, power, clock), and shapes (routing, pins, blockages, rows, tracks).
• Focus nets — Isolate specific nets for inspection, dimming all other routing.
• Tcl console — Execute Tcl commands interactively from the browser.

The module has two parts:

• C++ server (src/web.cpp, src/request_handler.cpp, src/tile_generator.cpp) — A Boost Beast WebSocket server that handles tile rendering, object selection, timing/clock-tree queries, and Tcl evaluation. Tiles are rendered from ODB geometry and encoded as PNG using lodepng.

• JavaScript frontend (src/main.js, src/index.html, src/style.css) — A single-page application using Leaflet.js for the map and GoldenLayout for resizable panels. Communicates with the server over a binary WebSocket protocol.

# Start the web viewer, pointing at the web assets directory
web_server -dir /path/to/OpenROAD/src/web/src

There are a set of regression tests in ./test.

bazel test //src/web/test/...

BSD 3-Clause License. See LICENSE file.