What is speedglitch?

To put it simply, speedglitch is literally just the game running faster, similar to if you just turned up host_timescale. There are three tiers of speedglitch which I'll explain the meaning behind in a moment: 32, 34.5, and 36.3. This glitch only works on L4D1 1.0.0.5.

"32" is equivalent to host_timescale 1.06, "34.5" is equivalent to host_timescale 1.14, and "36.3" is equivalent to host_timescale 1.20. These can sometimes also be referred to as 6.1, 5.7, and 5.3 (the amount of seconds it takes between the scoreboard appearing and the next level load to start at the end of the level - normally, without speedglitch, this takes 6.5 seconds).

32/34.5/36.3 refer to the number of packets you are sending/receiving to and from the server as shown in the right side of net_graph (requires net_graph 1, and increased cl_cmdrate or increased cl_updaterate (or both) in order to see it here:

How do I trigger/"enable" speedglitch?

When you open your game, simply create a lobby. You don't need to load into a server, just entering a lobby is enough. After that, speedglitch can occur in any type of server (singleplayer, lobby or map command) until you restart your game.

How does it work/how do I use it in a run?

Certain levels will almost always (if not always) have the slowest speedglitch (32) upon loading in: Turnpike, Hospital, and Terminal. If you then die and restart that level, you will spawn in with the fastest speedglitch (36). This applies for any case where you have 32 speedglitch - if you die and restart the level, you should get the 36 speedglitch when you respawn. Otherwise, if the level started at normal speed, then you will most likely get 34.5 speedglitch after you die. The speedglitch will last until you transition to the next level.

Note: According to a message in the discord from @JurasPatryk , there is about a 50% chance of getting speedglitch on most levels in the game, but if you start on No Mercy, then there is a 99% chance you will get it on the finale. Unsure if this means you'll load in with 32 or just have good odds at getting 34 if you die and respawn at the start, but yeah.

Generally, you will only want to purposefully kill yourself to activate it on long levels (Hospital, and every finale), as those are the only places where the game running faster is worth the time taken to die and restart the level when you load in.

How do I avoid speedglitch?

If you don't want to run speedglitch, don't ever enter a lobby. If you want to run no speedglitch co-op, you will need to use a map command server and port forward (or use alternative networking methods like Radmin VPN... or Hamachi 🤮), then connect via your friend's IP address.