Why does my forum’s performance suck?

With growth or just with the passage of time, phpBB forums can slow down. Pages may take a while to load if they load at all. You might get HTTP 500, 403 or other errors.

Today, site visitors expect fast response and if they don’t get it they may just decide it’s not worth coming to your forum. However, troubleshooting the root cause of these problems can be hard.

Often just opening a support ticket with your web host will bring you resolution. Or not. Web hosts run the gamut from poor to excellent, and generally the less you pay the poorer the service is. Web hosts though often know what the problems are, they just don’t want to tell you, as it makes them look bad. They may want you to pay for a higher quality of hosting to “solve” a problem that is really their fault, because they don’t maintain their infrastructure properly.

Here are some reasons that may be at the heart of your forum’s performance problems:

  1. Increased traffic. The traffic may not be traffic to your forum, but to other websites hosted on the same machine (server) as your website, if you are using shared hosting. This used to be a huge problem. Hosts would overload servers with domains because it was cheaper than going out and buying new machines. This works for a while until enough customers complain. The smart customers rehost somewhere else but obviously their hosts are hoping the rest won’t bail because it’s too much hassle. If traffic is getting consistently slower over a relatively short period of time or you are seeing a consistent increase in 500, 403 or similar error pages while using shared hosting, this is probably the reason. If your site is getting massively more traffic than you did before you might need to upgrade your hosting to a virtual private server or possibly even a dedicated server. Web hosts usually provide reports on usage that will help you get an idea if this might be the cause.
  2. Old hardwareThe law of entropy states that over time systems must degrade, i.e. become more complex or inefficient. It happens to your host’s servers too. Your website may be on a server that is ten years old, or has insufficient memory or CPU power for today’s needier software. So work may go into a queue until the CPU can catch its breath. While you are waiting of course nothing is happening. One clue may be to check the software installed on a server. For example, if you look in phpMyAdmin and you find that your MySQL database is running version 5.1 (released in 2008) then maybe your server is 2008 vintage, or older. Today MySQL 5.5 is generally the minimum version installed, with 5.7 being the newest and shiniest.
  3. Underpowered servers. Your server may not really have sufficient resources (CPUs, disk drives, etc.) to handle the traffic that is on it.
  4. Resource limitations. With shared hosting in particular there are implicit and generally poorly understood limits on the number of “resources” you can use: files, memory, CPU time or units of database work. You will usually see errors like this when they happen. They mean generally two things: either you are outgrowing your hosting or your server is overcommitted with other domains it is supporting. If your traffic is pretty steady, it’s more likely the latter problem. This is a sign of a poor host. You might want to rehost.
  5. Dated software. I mentioned that a host still running MySQL 5.1 is a yellow flag of caution. It’s not that MySQL 5.1 was a bad version, but many new features and performance improvements have been added since 2008. Your forum’s software has probably gotten more complex so it could use those improvements. Similarly, hosts running PHP 4 (fortunately, there are very few of these left) or even PHP 5.2 need to update their technology stack. You can see your version of PHP, web server software, operating system and the database in the Administration Control Panel, PHP information. Even the web server software you use can be dated. Still on Apache 1.2? You should probably be hosting somewhere else.
  6. You’ve been hacked! This happens rather infrequently, but it does occur from time to time. Malware or other bogus code may have infected your phpBB programs, templates and stylesheets, chewing up CPU and worse possibly infecting your readers’ computers with malware. Needless to say any malware must be removed. It may be discovered by comparing your software with a reference version of phpBB that you are using.
  7. Your database needs tuning. With so many reads and writes, your database may have grown and scattered itself all over the server’s disk platters, making it time consuming for the database management system to read and write data. You can try repairing and optimizing your forum’s tables in phpMyAdmin or a similar tool and see if performance improves.
  8. Your database is not properly configured. You may be missing primary keys, or indexes for tables. In some cases certain standard columns (added with upgrades) end up missing. Primary keys and indexes are used to retrieve data quickly. If they are missing the database won’t complain, but it will read all rows in a table to get what it needs, which is highly inefficient and can make a forum crawl. These sorts of problems are often the result of database updates that never finished properly, although they may have said they did. This can happen frequently upgrading from phpBB 3.0 to 3.1.
  9. Your phpBB version is woefully out of date. I am still surprised by requests that I get to upgrade phpBB 2 forums. phpBB 3.0 was released in late 2007! The problem is often not phpBB 2 itself, but your PHP version, which has evolved, making the handshake between PHP and phpBB awkward and inefficient, if it doesn’t trigger PHP warnings or errors. Upgrades are never fun or painless, but something you need to keep up on.
  10. You need to use a different database. Typically phpBB is used with the MySQL database because it’s free. phpBB at least in theory supports a host of other databases including SQLite and SQLServer. Most of the testing is done against MySQL and really phpBB is optimized for use with MySQL or its clone MariaDB. You will probably see better performance if you stick with these databases.
  11. You are using Microsoft software on the server. IIS is Microsoft’s web server. If you are running IIS you are also on a server using a Microsoft server operating system. IIS is not a bad web server but it works suboptimally with phpBB. phpBB should work best in a standard environment. So if you have the option to move to a Linux/Apache web server you may find marked performance improvement.
  12. Your browser is old. phpBB expects a reasonably modern browser. If others aren’t having issues but you are, maybe it’s time to upgrade your browser from IE7 or Firefox 2. Stick with recent versions of browsers like Firefox, Chrome, Safari and Opera.

There are other reasons your forum could be slow, but most likely the cause is one or more of the above. If you don’t feel you have the expertise to troubleshoot these issues yourself, or simply would rather have it done professionally, send me a service inquiry.


If you administer a phpBB board, you should find my book Mastering phpBB Administration invaluable. Learn lots of tips, tricks and secrets I learned from serving over 400 clients. A paper (7.5 x 9.68 inches) and an ePub version are available.

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