When my clock runs on my opponent's turn, Chess.com doesn't offer a fair game of chess, sad to say.  Fix the glaring software bugs and I'll consider subscribing.

What is Lag Forgiveness? (Why did the clocks suddenly change?)

Don't worry - the clocks are not broken. This jumping is caused either by bonus time(increment) or because of Internet lag.

In the case of internet lag, Chess.com (and most other chess sites) does something called 'lag forgiveness' where the time it takes for a move to travel to and from our servers is added back to the clocks.

Here is how lag forgiveness works on Chess.com:

When you make a move, the move has to spend some time traveling to our server, and then from our server to your opponent's computer. We adjust the clocks dynamically so that neither player is "charged" for the move's travel time - but rather, only for the time actually spent thinking.

Just to get a clear picture, let's imagine a very bad lag situation:

Imagine there is some very bad lag going on, and it takes 1 second for your move to get to our server, then another 1 second for the move to get to your opponent's computer from there. 

In this case, your opponent will not see this move until 2 seconds after you made it, but your opponent's clock will start counting down on your screen when the move hits our server. 

Then, let's say your opponent thinks for a total of 10 seconds, then plays a move. His move will take another 1 second to get to our servers, and another 1 second to go from our servers to your computer.

So, you have been waiting for this move for roughly 14 seconds (2 seconds travel time, 10 seconds thinking time, and another 2 seconds return travel time), and your opponent's clock on your screen has been counting down for roughly 14 seconds. 

Chess.com believes that it's unfair to charge someone for all that travel time! Since your opponent only spent 10 seconds thinking, that's all the time they get charged for. So, when their move finally hits your computer, their clock display adjusts for the 4 extra seconds that your opponent wasn't actually thinking. 

Meanwhile, your clock display on your end will only count down while you are thinking. There is no need for correction on your end, but on your opponent's screen they will be seeing the same adjustment to your clock, and possibly thinking there is something fishy going on there, if they haven't read this article!

This lag or 'travel time' is what gets added back to your opponents clock AND your clock during games. Usually the travel time is very low, so you won't notice anything. But when someone has bad lag it can make it seem like the clocks are behaving badly! 

Fortunately, travel times are usually less than what is described above. However, the travel times are not consistent, so adjustments must be made dynamically. 

There is no way around it: all real-time chess servers have to deal with lag, though other sites are a bit less transparent about it!

How it works, the details

The above description is how it works if we're talking about a single move with bad lag, but Chess.com doesn't forgive an unlimited amount of lag! If you have 1+second lag for multiple moves in a row, you will notice the lost time on your clock. And there are different limitations for different time settings, too. Here's how it works:

For the Rapid time setting, Chess.com will forgive a minimum of 500ms (500 milliseconds is 1/2 of a second) for each move you make. This means that if your lag is 500ms or less and you are playing Rapid, you won't notice a thing. 

In addition to the 500ms per move, you also get a bank of 1000ms to use over the course of two moves. This means if you have lag of up to 1500ms for a single move, it will all be forgiven. But if on the following move you still have the same lag of 1500ms, only 500 will be forgiven, and the remaining 1 second will be lost. 

In other words, you will always be forgiven for at least 500ms on every move, and you also have a backup of 1000ms to use if needed, which refills every other move. Because of this bank of 1000ms, you could have a lag of one full second every move, and not notice anything. For example: 

Move 1, a lag of 1000ms. 500ms is canceled automatically, then another 500ms is canceled out of the bank. This leaves 500ms in the bank. 

Move 2, a lag of 1000ms again. 500ms is canceled automatically, then another 500ms is canceled out of the bank. The bank is now empty, but at the end of move 2 the bank is refilled back to 1000ms again. 

All the above, however, only applies to Rapid chess. For other time settings, the minimum and the bank are different sizes: 

RAPID (described above): 500ms per move + 1000ms bank per 2 moves. 
BLITZ: 300ms per move + 400ms bank per 2 moves. 
BULLET: 200ms per move + 100ms bank per 2 moves. 

If you notice that you only experience lag while playing bullet, this may be why. Bullet is much less forgiving of lag! 

If the information in this article is out of date, incorrect, or unclear, please let us know!

Keywords: clocks, skip, clock, jumping, time, cheat, delay, bonus

I'm playing on half gig fiber. Your own lag meters says I have no lag. And yet I lose 10 seconds randomly on one turn.

Chess.com is just broken. Your own post proves it. I have no lag according to your site. Full bars. Yet your *server* is lagging.

It's chess.com's own servers that prevent fair and equal chess games.

Lag can be caused by a number of factors, including processes running on the local client device and local network.
There are some things that can be done to minimize issues on that end.

https://support.chess.com/article/4720-online-chess-performance-optimizations

That said, there are things between your network and the site servers that can also impact connections and introduce lag.

Did you bother reading what I wrote before you copy pasted?

I said your lag meter says I have no lag, and yet my clock is running on my opponent's turn. Are you saying your lag meter is broken? If so, how are you so sure your servers aren't also having issues?

What metrics do you use to monitor the servers? How are you confident they aren't having problems? Given the number of times your server throws up 50x errors, and posts a picture of a guy unplugging a neon chess piece, I think your answers are misplaced in blaming me.

Let me guess, if I paid you guys money, I'd magically get my moves higher priority int he server queue and I'd win more games. It's a pretty standard mobile game model: free to play, pay to win.

If the lag meter is full, that means "very low lag", not "no lag".

When you make a move, it doesn't immediately register on your opponent's computer. It takes some time, even if a very small amount of time. The farther away you are from the server, the more time it will take. That's just how the internet works. Deal with it.

It literally says.very low latency.

So you admit it yourself. Very low latency, not no latency.

Yes, not 4 seconds of latency, yet I lose 4s/move on premoves, which according to the published rules should only lose 0.1s/move.

So the issue is proven not to be my browser, or my network connection, but rather the server queue that processes moves on chess.com's servers.

When the servers are having issues, which isn't common, then pretty much everyone is impacted and staff are aware of the issues. I'm not certain how well the lag indicator is but as far as I'm aware it's basically a small packet, like a ping. There's a lot more data going back and forth between you and the server and client/local network lag might might not impact that as much.

I'm also not blaming you but network communications have a lot of variables, some within your control, some within the site's, and a lot that can't be controlled.

As to premium, the main difference is that you don't get the advertisements, which can have some impact on connectivity on occasion.

Premoves take a minimum of 0.1 but can take longer. If you're seeing that kind of move timing on premoves, there is something between you and the site causing issues (assuming nothing on the client or local network causing it).

Any lag introduced on one client side will have no impact on their opponents, if that's what you're suggesting.

too many people, are too hyped up.

Lately when I start a game, my clock is suddenly several seconds behind my actual game play. This morning I played a few games in a row during which my clock would suddenly jump 5 to 10 seconds behind (I would make a move in 1 second and the clock showed that 10+ had gone by), and my opponent's clock would continuously jump back in time by 10 and more seconds.

That would make a lot of sense, if it's trying over and over again to load ads, it could clog up the browser window's process queue.

Yeah it's really funny how on lichess the exact same phone, exact same connection doesn't have multi-second lag when I try to make moves. My losses are from play, not having to give my opponent 50% time odds.

So it's definitely some combination of Chess.com's ad code, and their internal latency, that's the issue here.

Pretty sure Lichess basically allows pretty much all lag, so if you have issues, it doesn't impact the clocks. It's a fundamental difference in how lag is handled between sites.

Disappointed to see Chess.com posting misinformation about competitors. Lichess has the same kind of lag compensation your site has. It's just that their servers and client software are better than yours.