BAGEL

BAG ExpLoration: ROS Bag File Web Visualizer

Explore ROS1 & ROS2 bag files in your browser. No installation required.

→ Live Demo · Report Bug · Request Feature

What is BAGEL?

BAGEL is a fully static web application that lets you explore ROS bag files (.mcap, .db3, .bag), standalone point cloud files (.pcd, .ply), and 3D Gaussian Splat scenes (.ply, .splat, .ksplat) entirely in your browser needing no server, no installation, no account. Just drag and drop!

Robotics engineers and researchers frequently generate bag files during experiments, SLAM runs, and sensor calibration. Inspecting these files currently requires a full ROS1 or ROS2 installation, Foxglove Studio (increasingly commercial), or writing custom Python scripts for every inspection task.

BAGEL eliminates this friction.

Why BAGEL?

Demo

Quick tour with the bundled sample bag

Stress test with a real-world SLAM dataset

Data featured in this demo is from the excellent open-access M2DGR dataset provided by the SJTU-ViSYS team, which was instrumental in stress-testing this visualizer's spatial rendering capabilities.

Features

A condensed feature list is below. Detailed version-by-version release notes (with the design rationale behind every feature) live in FEATURES.md.

File formats and live sources

Visualization panels

• TimeSeriesPlot: chart any numeric leaf field (linear.x, orientation.w, etc.) on uPlot. Math expressions as derived series: type field_a * 2 + field_b in the series editor to plot any arithmetic combination of fields from the same topic without writing code. (v1.4.1)
• ImageViewer: sensor_msgs/Image (rgb8 / bgr8 / rgba8 / mono8 / mono16) and CompressedImage (jpeg / png) with lazy single-message reads. Foxglove equivalents (foxglove.RawImage, foxglove.CompressedImage) supported via JSON schema translation. (v1.6.1) H264/H265 video via foxglove.CompressedVideo using the browser's WebCodecs VideoDecoder with a fast keyframe index for efficient seeking. (v1.6.2) Scroll to zoom (cursor-centered), drag to pan, double-click to reset; zoom percentage shown in the footer. (v1.6.3) Optional sensor_msgs/CameraInfo overlay (principal-point reticle + focal-length badge + calibration-likely-unfilled chip) toggles from the panel header. (v1.3.2) undistort button applies per-frame plumb-bob (Brown-Conrady) undistortion using the paired CameraInfo's D coefficients. (v1.3.4)
• ThreeDScene (Three.js): PointCloud2, LaserScan, MarkerArray (all twelve primitives: CUBE / SPHERE / CYLINDER / ARROW / LINE_STRIP / LINE_LIST / CUBE_LIST / SPHERE_LIST / POINTS / TEXT_VIEW_FACING / MESH_RESOURCE / TRIANGLE_LIST from v1.3.1), OccupancyGrid, pose markers, camera frustums for every sensor_msgs/CameraInfo topic with per-camera hide checkboxes on multi-camera rigs (v1.3.2 / v1.3.4). Custom orbit pivot, range filter, point accumulation, configurable up-axis.
• Spatial topic layers (v1.7.1): Open any 3D panel, then use Display > Overlays > scene topics to add maps, point clouds, laser scans, and odometry or pose topics to the same TF-aligned scene. This supports workflows such as an OccupancyGrid base map with live LiDAR points and the robot odometry pose on top. Per-overlay point size and flat-color overrides keep stacked layers visually distinct. A top-down orthographic 2D projection mode (with a zoom slider synced to scroll/pinch) reads an overlaid scene like a floor plan instead of a 3D orbit.
• SplatViewer (v1.7.0): dedicated 3D Gaussian Splat renderer for splat-flavored .ply / .splat / .ksplat files, built on @mkkellogg/gaussian-splats-3d. Outlier-robust camera auto-fit (ignores stray "floater" splats a naive bounding-box fit would get wrecked by), shift+click custom orbit pivot, and keyboard fly-through: W/S forward-back, A/D strafe, Q/E turn, R/F up-down, Z/C orbit around the pivot, active while hovering the panel. B/N, I/K, U/J spin the splat itself around the pivot on the Z/X/Y axes respectively, instead of moving the camera - useful for viewing it from a new angle or correcting a multi-axis tilt without the camera's perspective changing. V cycles up-axis orientation presets, since gaussian-splatting exports don't follow one universal up-axis convention.
• TrajectoryPlot: Odometry / Pose / PoseWithCovariance / TransformStamped / NavSatFix as a 2D polyline, with an opt-in OpenStreetMap tile underlay for GPS traces.
• TFTree: /tf + /tf_static hierarchy with current transforms at the playhead time.
• DiagnosticArray: swimlane timeline + at-playhead inspector for diagnostic_msgs/DiagnosticArray. (v1.0)
• Log (rosout): virtualised list for rcl_interfaces/Log and rosgraph_msgs/Log with severity, node-name, and full-text filters. (v1.0)
• RawMessageInspector: collapsible JSON tree of the deserialized message at the playhead.

All panels resolve header.frame_id through /tf + /tf_static against a user-selected world frame.

Multi-bag overlay

• Drop multiple bags into the same session; each gets a colour tint that flows through every panel.
• Three time-alignment modes: wall-clock, bag-start, and anchor (with a "Set anchor" picker UI in v1.0 so you can lock runs to a physical sync event).
• Per-bag parser Web Worker so parsing bag B doesn't queue behind bag A's decode.

Layout, sharing, and export

• Drag-to-dock VSCode-style panel layout. Per-panel state (3D display settings, plot zoom, TF selection) survives docking.
• Sharable URL hashes encode layout + playhead + bag URL + per-bag anchors. v0.5 / v0.7 / v0.9 hash forms still parse, so old links keep working.
• Per-topic CSV / NDJSON export from every panel header.
• Bag editing / MCAP clip export: trim the time range, drop topics you don't need, download a fresh indexed .mcap. Replaces the mcap filter CLI workflow for the common cuts. v1.2 extends the editor to ROS1 .bag and ROS2 .db3 inputs alongside MCAP - output is always MCAP regardless of input format. .db3 topics whose type isn't in BAGEL's bundled registry are flagged in the modal and excluded by default; opt them in to include them with a schema-less channel. (v1.1 / v1.2)
• Paste-your-own .msg schema flow for ROS2 .db3 topics whose types aren't in the bundled registry. Persisted across sessions in localStorage.
• Clip export: Export button in the Toolbar renders any open panel (Image, Plot, Trajectory, or 3D Scene) frame-by-frame to a PNG zip or WebM video. Uses a frame-sync protocol (seek playhead, 2x rAF + 250 ms settle, canvas.toBlob()) so every panel type captures correctly. PNG frames are zipped with fflate at level 0 (no re-compression of already-deflated PNGs); WebM uses a two-phase MediaRecorder + captureStream(0) + requestFrame() approach so video playback speed is always correct. (v1.4.2)
• Timeline bookmarks: drop named markers at any timestamp on the scrubber (double-click the bar, click the + button, or press M), click a tick to seek, hover to see the label. Bookmarks persist to localStorage per bag and are encoded in the URL hash (bm=) for sharing. (v1.4.3)

Robot model (URDF) overlay (v1.3.0)

• Drop a .urdf and the robot appears in every 3D panel, anchored to its root link in world space via the bag's /tf stream. Joints animate from sensor_msgs/JointState (auto-detected) when the bag publishes it; static URDFs render at their rest pose. A toolbar "Robot" button opens the load modal; the Display card in each 3D panel grows a per-panel robot model hide toggle.
• Geometry support: box / cylinder / sphere primitives + .stl / .dae / .obj meshes. Loaders are lazy-imported on first use of each file type so primitives-only URDFs don't pay the Collada loader's bundle cost.
• package:// resolver: paste a URL prefix or drag-drop a folder per referenced package; URL bindings persist across sessions in localStorage under bagel:package-roots:v1. No auto-fetch from ROS distros - BAGEL only loads meshes from where you point it.
• Bundled sample robot URDF (public/sample-bags/sample-robot.urdf) pairs with tour.mcap so the "Try a sample robot" button in the modal demonstrates the full flow on a fresh checkout.

Live robot data (v1.5.0 - v1.5.6)

• Foxglove WebSocket client: connect to a live robot by pasting a ws://host:8765 URL into the new "Connect" input. Works with foxglove_bridge (ROS2) and rosbridge_suite (ROS1/ROS2). Implements foxglove.websocket.v1 - binary MESSAGE_DATA frames for message payloads, JSON frames for topic advertisement.
• Per-topic ring buffer: the last 10,000 messages per topic are held in memory. All existing panels (Image, Plot, 3D Scene, Trajectory, TF Tree, Log) display live data without any panel-level changes - the hooks detect a live entry and read from the ring buffer instead of the parser worker.
• Follow / Pause mode: the timeline's Follow button (also in the Toolbar chip) keeps the playhead at the live edge. Press Pause to scrub back through buffered history; press Follow to snap forward again.
• Auto-reconnect: exponential backoff on disconnect: 1s, 2s, 4s, 8s, 16s, 30s. Connection status shown as a pulsing dot (emerald = connected, amber = reconnecting, rose = error) on the toolbar chip.
• CDR and JSON decoding in the main thread. ROS2 CDR via @foxglove/rosmsg2-serialization, ROS1 CDR via @foxglove/rosmsg-serialization - both already bundled as bag-parsing dependencies, no new packages. (v1.5.3 adds encoding: "ros1" for ROS1 bridges)
• Live MCAP recording (v1.5.2): Record button in the Toolbar (visible when a live connection is active) buffers every incoming message. Click Stop to serialize all captured data to a fully-indexed MCAP file and download it instantly. The output opens back in BAGEL or any mcap-compatible tool without conversion.
• Recording size limit + topic filter (v1.5.5): 500 MB hard cap auto-stops the recording and downloads immediately. A filter icon lets you select a subset of topics before recording starts. Byte count turns amber above 400 MB as a warning.
• Sim clock support (v1.5.4): when /clock is advertised, messages with logTimeNs = 0 (common in Gazebo/Isaac Sim) use the simulation clock value instead of wall-clock time, keeping plots readable in simulati