"Dropped frames" means that your connection to remote server isn't stable or you can't keep up with your set bitrate. Because of this, the program was forced to drop some of the video frames in order to compensate. If you drop too many frames, you may be disconnected from the streaming server.
Speed tests provide very rough estimate - they mean very little with regards to streaming. Just because a speed test says you have 5 Mb/s upload doesn't mean you can upload to anything at a stable 5Mb/s since connections across the internet rarely maintain such a consistent speed.
Your "stable" bitrate is more likely about 70-75% of your "estimated" speed test upload (and that's only if you're not being throttled). If anything, a speed test will tell you the theoretical maximum speed that you could stream at under perfectly ideal conditions, but conditions are never perfect.
Possible reasons for dropped frames are:
It is nearly impossible for OBS Studio to cause dropped frames. Bear this in mind if you have recently updated OBS Studio and believe it is the cause of your dropped frames.
For a detailed, technical explanation on what dropped frames are, please check this post written by Jim.
OBS Studio 24.0 introduced a new feature called Dynamic Bitrate. This feature detects when your internet connection is limited, and will automatically reduce your bitrate to compensate rather than dropping frames. Once any congestion disappears, it will automatically raise your bitrate back to its original value.
To enable Dynamic Bitrate, first ensure you are using OBS Studio 24 or higher by looking at your version number in the title bar of the program. Then, go to Settings > Advanced > Network and check the box next to the option that says "Dynamically change bitrate to manage congestion".
Network conditions aren't always the same from day to day; what worked yesterday is not guaranteed to work today. The bitrate you have selected may be too high for the current conditions.
Settings -> Output -> Streaming.
Settings -> Video.
The server to which you are streaming might be overloaded. Switching another server will resolve many dropped frames/connection issues. Even the server the appears to be located closest to you or is shown to have the lowest ping may not give you the best connection. In fact, there have been times when Europeans have found US servers more reliable to stream though than ones located in Europe.
It can be helpful to try a different streaming service just to make sure the issue isn't with the stream service you're using.
The optional network optimizations setting makes OBS use an event-based API instead of non-blocking sockets. While this should technically behave no differently to the regular network code, some users have reported that this helps with their dropped frames or disconnection issues. The network optimizations code also includes detailed logging of network events which can help when you're posting a log file.
Settings -> Advanced -> Networkand click Enable network optimizations.
Note: this setting is not available on macOS.
In Settings -> Advanced, there is a setting to Bind to IP. By and large, this should be left at Default and not changed unless you know exactly what you are doing and why you need to. Make sure the setting is correct (this usually means Default). If you bind it to a specific IP address, and then that IP address changes on your PC, OBS Studio will fail to connect to any services.
Settings -> Advanced -> Network -> Bind to IPto Default.
In some cases, anti-virus or firewall/security software can interfere with the connection.
The process for adding disabling your network and/or adding an exception will vary. Please consult the software vendor's website for instructions. Remember to add exceptions for both 32 bit and 64 bit versions of OBS Studio.
In rare cases, some software/drivers/programs claiming to "optimize" or "enhance" your network connection can actually cause more problems. For instance, they might try to configure things that help with a game; however, that configuration might interfere with OBS Studio's operation.
Examples of network software interfering with normal performance include:
In some rare cases, dropped frames can be caused by an old network adapter driver doing a poor job of handing the high speeds being consumed.
In many cases, Wi-Fi connections can cause issues because of their unstable nature. Streaming requires a stable connection.
If you are getting disconnected and you've already tried other servers, check that your firewall/router/antivirus software is not interfering with the connection.
Note: you do not need to use any kind of port-forwarding to stream.
As a cause of dropped frames, faulty hardware is usually quite rare. This can include the router, any repeaters, the network card in your computer, or even the cabling. If you have another network card available (including the one in a laptop or other PC you might have lying around) try that plugged into the modem to check for network card problems on your streaming PC. Try using different Ethernet cables too.
Remember, OBS is unlikely be the direct cause of connection issues or dropped frames. If you have tried all of the above and still have issues, the problem may be out of your direct control.
It is common for Internet Service Providers (ISPs) to run maintenance or change things on their end that can cause you as a subscriber to have issues. Your connection may also be throttled by the ISP.