Open the demo viewer, sign in with Steam, and upload your Counter-Strike 2 .dem file. The server parses it into map data, player snapshots, round and kill events and grenade trajectories, then the browser rebuilds the match in real Source 2 map geometry. You watch it with a timeline, five camera modes, a radar, an event feed and a match review panel.
What do you need to watch a CS2 demo online?
A CS2 demo is a recording of match state — positions, view angles, health, weapons, money, round and kill events, grenade throws — written by the game server, not a video. Because it is state rather than pixels, it can be replayed by any renderer that understands it. That is what makes browser playback possible at all.
You need three things:
- The file. A Counter-Strike 2 demo, usually ending in
.dem. If your download arrived as an archive, extract it first — see how to find and download a CS2 demo. - A browser with WebGL. The replay is rendered in 3D on your machine. Recent desktop and mobile browsers qualify; there is no separate demo client to install and nothing to copy into a CS2 folder.
- A Steam sign-in, for your own demos. Uploads, pasted match links, the one-a-day quota and demo ownership are all attached to an account. The daily Replay Moment is playable with no account at all if you only want to see how the viewer feels first.
Step-by-step: upload and watch
- Open the demo viewer. The front page is the dashboard, not a marketing gate.
- Go to Matches. This is the match list and the upload area.
- Add the demo. Drop a
.demonto the upload area — compressed files are accepted too. Where the server integration is configured, you can instead paste a CS2 matchmaking share code or a FACEIT match link and let the server fetch the demo, so nothing large leaves your machine. - Wait for parsing. The server walks the demo once and writes a cache: match metadata, a binary snapshot stream, and grenade data. Longer matches take longer; this is a one-time cost per demo, and reopening it later is immediate.
- Open the match and navigate. Use the timeline, the speed selector (0.25×, 0.5×, 1×, 2×, 4×, 8×), the seek-interval selector (1, 5, 10 or 30 seconds) and the view selector. Press R for the review panel and Tab for the scoreboard.
What does the browser replay actually reconstruct?
A browser demo viewer is only useful if the reconstruction is faithful enough to answer a question about the round. Here is what is rebuilt from the parsed demo:
| Layer | What you see |
|---|---|
| Map | The real Source 2 geometry for the map, with baked lighting, skybox and environment configuration per map — not a simplified box model or a flat radar image. |
| Players | Position, view angle, health, armour, crouch state, active weapon and money, sampled from the demo every two ticks (32 snapshots per second on a 64-tick demo) and interpolated between samples. |
| Events | Rounds, kills, bomb plants and defuses, and the kill feed with the official extracted CS2 weapon and headshot/wallbang/no-scope/smoke modifier icons. |
| Utility | Grenade throws by round and type, complete trajectories, and detonation or landing detail. Smokes render as real volumetric smoke driven by the voxel data recorded in the demo, not a billboard sprite. |
| HUD | A CS2-style scoreboard, team rosters, the round timer and alive counters, and a first-person HUD with health, armour, ammo, money and the loadout stack when you sit in POV. |
Which camera should you use?
The view selector offers five modes, and the difference between them is the difference between a good review and a hindsight-driven one.
- Player POV shows the match from one player's view angles. Use it first, to establish what information that player actually had.
- Follow player is a chase camera behind the player — easier to watch for long stretches than POV.
- Free camera flies anywhere in the map. Use it second, after POV, to see the situation the player could not.
- Top-down is the tactical view for spacing, rotations and route timing.
- Multiple POVs renders up to ten player views at once. Individual feeds can be hidden, and one-click CT/T presets give you a five-man side view.
Press F to cycle free → follow → POV → top-down, and the number keys to select a player. The full list is in the CS2 demo viewer controls and keyboard shortcuts reference. Two extra layers help when a route is ambiguous: X toggles x-ray player outlines through walls, M toggles the radar, and B drops you into walk-the-map mode so you can move through the map yourself at player height.
Which CS2 maps are supported?
Ten maps have the extracted geometry, lighting and radar calibration needed for a reconstructed match: Ancient, Anubis, Cache, Dust II, Inferno, Mirage, Nuke, Overpass, Train and Vertigo. A demo on a map outside that pool is rejected rather than rendered with missing geometry. The per-map review considerations — including the two-level radar on Nuke, Train and Vertigo — are covered in the CS2 map review guide.
What browser demo playback does not do
A reconstruction is not a screen capture. The replay renders recorded state through this viewer's own renderer, so it is not pixel-identical to what the player saw: their crosshair settings, video options, resolution, personal HUD and voice communications are not in the demo. Older cached demos may also carry fewer fields than newer ones; when a value such as ammunition is genuinely absent, the HUD shows a dash instead of estimating it. The full boundary is written up in what a CS2 demo analyzer can and cannot tell you.
What to do after the first watch
Watching is the cheap half. Start with the rounds that decided the match, and use the structured workflow in how to review a CS2 demo so the session ends with one testable change rather than a general feeling. When a death is worth more than a rewatch, open it as a Replay Moment: the situation is rebuilt with the real positions, utility, health and clock, and you take control and play it yourself.
Frequently asked questions
Can you watch CS2 demos without installing anything?
Yes. Memorin parses the demo on the server and renders the match in your browser using WebGL, so there is no demo client, no CS2 installation and no launch option to configure. A modern desktop or mobile browser is enough.
Do I need a Steam account to watch a CS2 demo online?
You need to sign in with Steam to add your own demo — whether you upload the file or paste a match link, both go through the same account. Acquisition, quota and demo ownership are tied to an account. The daily Replay Moment is playable with no account at all.
How long does it take to parse a CS2 demo?
Parsing time scales with the length of the match and the size of the file rather than a fixed number. A full competitive match takes noticeably longer than a short one, because the parser walks the whole demo once to build snapshots, round boundaries, kill events and grenade trajectories.
Which CS2 maps can I watch demos on?
Ten maps have the real Source 2 geometry and radar calibration needed for a reconstructed match: Ancient, Anubis, Cache, Dust II, Inferno, Mirage, Nuke, Overpass, Train and Vertigo. A demo on an unsupported map is rejected rather than shown with missing geometry.