1. Try another browser
2. Try from another computer with http://anonymouse.org/anonwww.html or http://www.downforeveryoneorjustme.com/ (your IP could be blocked or something)
3. Use Tiki Check to detect issues.
4. Check for BOM in your files
5. Check release notes for your version and the previous ones — is this a known issue?.
6. Check the reported bugs — is this a reported issue?
7. Are you running latest stable version? Your Tiki version is shown on the General Admin page.
8. Is database out-of-date? Starting in version 3.0, Tiki will report a Database Version Problem message on the Admin Panels if your database requires an update.
9. Is your database corrupt? See Repair database for details.
10. Clear all Tiki caches by selecting Admin > Tiki Cache from the menu.
11. Deactivate GZIP, Minify, and other options in the Performance admin panel
12. Deactivate Apache Clean URLs (especially if you are on Windows IIS server). If this solves the issue, it's likely because you are using an old version of .htaccess instead of the one for your version of Tiki.
13. Clear your browser's cache by using Ctrl+F5. Refer to your browser's help system for details.
14. Clear your browser's cookies. Refer to your browser's help system for details.
15. Try another browser, such as Firefox, Internet Explorer, Safari, Chrome, or Opera.
16. Check your web server's error log. Any file or folder permission problems are commonly shown in the log.
17. Are your Tiki file and folder perms configured properly? If you have shell access to the server, use sh setup.sh.
18. Attempt to log out of your Tiki, then log in again.
19. Check integrity of your files.
20. Have you added any custom entries to the .htaccess file? Temporarily comment them out.
21. If you changed a server setting, did you restart Apache?
22. Change the theme (especially if you are using a custom theme). See Tiki Themes for details.
23. Try to reproduce the problem on a Tiki demo site. If you can reproduce, then, please report a bug.
24. Enable the Tiki debugging features by applying the Debug Mode Profile.
25. Check in MySQL for the table tiki_actionlog to see what the latest changes were before the issue started.

Be sure to review the Tiki FAQs for answers to frequently asked questions.

...and I can't go to profiles to enable Debug Mode
Try:

• Run the installer at tiki-install.php
• In one of the steps, you can activate error messages

Or

1. Access your database (by using Adminer, phpMyAdmin or the equivalent).
2. Find the table tiki_preferences.
3. Edit the values from above.

• Item: error_reporting_level
• Value: 2047

mysql -h localhost -udbusername -p*********** dbname -e "UPDATE tiki_preferences SET value = '2047' WHERE name = 'error_reporting_level'"

You should also empty the Tiki cache or manually delete all *.tpl files in the ../templates_c/ directory.

Please note that some server configurations will prevent Tiki from overriding the error reporting of PHP. Make sure your server has error reporting and/or logging properly setup.

If your Tiki is in a subdirectory and you use HTTPS, this forum thread may be some help.

This could be because of ModSecurity, which you should turn off temporarily.

The most common cause of a blank screen in which Tiki shows no error message and no content is insufficient PHP script execution memory. Tiki requires a minimum of 64MB (the default value of PHP 5.3 is 128 Megs and ideally, it should be at this value). (which you can change in php.ini or httpd.conf. If you are using OPcache, APC or XCache, make sure they also have enough memory.

Also, make sure to activate your error messages. You can do this be re-running the installer at tiki-install.php (Step #7 Configure the General Settings)

Review your tiki-phpinfo.php page or contact your server admin to make sure your site meets this requirement. See Requirements for details.

Blank pages after inserting code

Another case of getting WSOD (or a "blank page") can happen when you insert some custom JS or CSS code containing curly brackets in the Look & Feel admin panel or custom module textareas and forgot to surround them with literal Smarty block:

{literal}...{/literal}

Let's assume, that you cut and pasted some code containing curly brackets in the Custom HTML Head textarea.

Now you hit the Apply button and suddenly. Eeek! You are "locked out" in the WSOD! But Do not panic™! There is a solution 😉

Actually, you have two options how to fix or reset it back:

1. If you do not want to loose the previous content of that textarea you just edited you can go to your MySQL admin tool (Adminer, PHPMyAdmin or whatever is available for you) and locate the feature_custom_html_head_content field (if it happened to be another textarea than Custom HTML Head, just look for the other one by similar name) in the tiki-preferences table. Then just edit the content of the field to fix it (e.g. by surrounding it by the literal block).
2. If you do not care about clearing and resetting that textarea completely, you can just use the following trick. In your browser's address bar instead of the tiki-admin.php?page=look put this there:
   tiki-admin.php?page=look&looksetup=Apply&feature_custom_html_head_content=&lm_preference[]=feature_custom_html_head_content
   Then hit Enter key on your keyboard and your Tiki should be back!

This can happen because of incorrect File and Folder permissions.

If you have lost or forgotten your Tiki admin password, see
Lost admin password.

Your Tiki may have trouble writing HTTP sessions to the disk. Instead, try storing in the database. In your lib/prefs/session.php file (you can see an example here, find the session_storage preference and change the 'default' from 'default' to 'db'.

If you customized a Tiki theme and now have problems, see Template Tricks on Tiki Themes.

If you created or edited a module and included invalid or poorly formatted syntax, Tiki may display errors. Access your database (for example, by using Adminer or phpMyAdmin) and remove the offending module from the tiki_modules table. Please note that you can easily re-instate via the admin panel after, as it is not deleted but just unassigned.

If you are getting weird error messages that no one else seems to be getting, it could that your upload didn't complete properly. So you are missing some files or they are corrupt. The solution is simple: reupload the files. Check file integrity

• Here is the error msg: XMLRPC Error: 5 - Didn't receive 200 OK from remote server. (HTTP/1.0 301 Found)
  • This happens with tiki.org is not available (with InterTiki login)

Ensure that there is no problem with the re-indexing. Check file indexing

This can be because there is no .htaccess, or it's there but the server doesn't support it somehow.

Solution: Turn off Search Engine Friendly URLs.

• This can happen if you are on a mobile device, that doesn't support CKeditor.
• If this is happening in a supported browser, it's likely because of invalid HTML. Try adding &wysiwyg=n to the URL, and then, clean up the data

This happened to me on an upgrade from Tiki 12.x to 18.x on a really old site with a lot of legacy data, specifically there were over 3 million rows in tiki_stats and feature_stats was enabled.

Each page load was taking a minute or so, and eventually i tracked it down to the index being missing on tiki_stats bacuse there was a duplicate value in the table that shouldn't have been there. So the process to find and fix it was:

/* to find the duplicate */
SELECT `object`, `type`, `day`, COUNT(*) AS anyVariableName FROM `tiki_stats`
GROUP BY `object`,`type`,`day` HAVING COUNT(*) > 1;

/* then assuming there is only one duplicate */
/* combine the two stats */
UPDATE `tiki_stats` SET `hits` = '2' WHERE `object` = 'Your Wiki Page Name' AND `type` = 'wiki' AND `day` = '1576627200' AND `hits` = '1' LIMIT 1;
/* delete the second one */
DELETE FROM `tiki_stats` WHERE `object` = 'Your Wiki Page Name' AND `type` = 'wiki' AND `day` = '1576627200' AND `hits` = '1' LIMIT 1;
/* add back in the missing index - note, this is for Tiki 18, 19+ should use `object`(157) due to utf8_mb4 */
ALTER TABLE `tiki_stats` ADD PRIMARY KEY (`object`(200),`type`,`day`);