BAGEL

BAG ExpLoration: ROS Bag File Web Visualizer

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

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What is BAGEL?

BAGEL is a fully static web application that lets you explore ROS bag files (.mcap, .db3, .bag) and standalone point cloud files (.pcd, .ply) 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.
• 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 simulation sessions. A SIM badge appears on the toolbar chip.
• Cross-bag health comparison (v1.5.6): the Health panel shows a chip strip at the top when multiple bags are loaded. Click any chip to switch the stats view to that bag without opening a new panel. Active chip is highlighted; live bags are excluded.

Analysis tools (v1.4)

• Bag Health dashboard (v1.4.0, extended v1.5.6): a per-topic analytics panel showing measured Hz, jitter (p50/p95 inter-message gap deviation), gap events (pauses longer than 3x the expected period), and bandwidth (bytes/s). Opens from a Health button in the Toolbar. Data is computed once per bag in a background scan and cached. (v1.5.6) When multiple bags are loaded, a chip strip at the top lets you switch the view between bags without opening additional panels.
• Math expressions in plots (v1.4.1): type arithmetic expressions (vel_x * 2 + offset, sqrt(x*x + y*y)) as derived series directly in the TimeSeriesPlot panel. References other numeric fields from the same topic; evaluated in a sandboxed expression engine (no eval).
• Clip export (v1.4.2): render any panel to an animated PNG zip or WebM video via a frame-sync protocol. Toolbar Export button opens the modal.
• Timeline bookmarks (v1.4.3): named markers on the scrubber, persisted per bag and shareable via the bm= URL hash segment.

UX and quality

• Light + dark themes (toggle in the toolbar; persisted per browser). (v1.0)
• Keyboard shortcuts: Space to play, ← / → to step, L to loop, M to bookmark (v1.4.3), Esc to close panels, T to focus topic search, O to open a bag, ? for the cheat-sheet.
• Loop playback: a Timeline toolbar toggle wraps the playhead back to start at end-of-bag instead of pausing, persisted across reloads. (v1.3.3)
• Saved Display defaults: per-data-type defaults for the 3D panel's Display card (colour mode, accumulator, point size, range filter, up a