One of the best ways to customize Bugzilla is by writing a Bugzilla Extension. Bugzilla Extensions let you modify both the code and UI of Bugzilla in a way that can be distributed to other Bugzilla users and ported forward to future versions of Bugzilla with minimal effort. See the Bugzilla Extension documentation for information on how to write an Extension.

Bugzilla allows you to have multiple skins. These are custom CSS and possibly also custom images for Bugzilla. To create a new custom skin, you have two choices: Make a single CSS file, and put it in the skins/contrib directory. Make a directory that contains all the same CSS file names as skins/standard/, and put your directory in skins/contrib/. After you put the file or the directory there, make sure to run checksetup.pl so that it can reset the file permissions correctly. After you have installed the new skin, it will show up as an option in the user's General Preferences. If you would like to force a particular skin on all users, just select it in the Default Preferences and then uncheck "Enabled" on the preference.

Administrators can configure the look and feel of Bugzilla without having to edit Perl files or face the nightmare of massive merge conflicts when they upgrade to a newer version in the future. Templatization also makes localized versions of Bugzilla possible, for the first time. It's possible to have Bugzilla's UI language determined by the user's browser. More information is available in .

The template directory structure starts with top level directory named template, which contains a directory for each installed localization. The next level defines the language used in the templates. Bugzilla comes with English templates, so the directory name is en, and we will discuss template/en throughout the documentation. Below template/en is the default directory, which contains all the standard templates shipped with Bugzilla. A directory data/templates also exists; this is where Template Toolkit puts the compiled versions of the templates from either the default or custom directories. Do not directly edit the files in this directory, or all your changes will be lost the next time Template Toolkit recompiles the templates.

If you want to edit Bugzilla's templates, the first decision you must make is how you want to go about doing so. There are two choices, and which you use depends mainly on the scope of your modifications, and the method you plan to use to upgrade Bugzilla. The first method of making customizations is to directly edit the templates found in template/en/default. This is probably the best way to go about it if you are going to be upgrading Bugzilla through CVS, because if you then execute a cvs update, any changes you have made will be merged automagically with the updated versions. If you use this method, and CVS conflicts occur during an update, the conflicted templates (and possibly other parts of your installation) will not work until they are resolved. The second method is to copy the templates to be modified into a mirrored directory structure under template/en/custom. Templates in this directory structure automatically override any identically-named and identically-located templates in the default directory. The custom directory does not exist at first and must be created if you want to use it. The second method of customization should be used if you use the overwriting method of upgrade, because otherwise your changes will be lost. This method may also be better if you are using the CVS method of upgrading and are going to make major changes, because it is guaranteed that the contents of this directory will not be touched during an upgrade, and you can then decide whether to continue using your own templates, or make the effort to merge your changes into the new versions by hand. Using this method, your installation may break if incompatible changes are made to the template interface. Such changes should be documented in the release notes, provided you are using a stable release of Bugzilla. If you use using unstable code, you will need to deal with this one yourself, although if possible the changes will be mentioned before they occur in the deprecations section of the previous stable release's release notes. Regardless of which method you choose, it is recommended that you run ./checksetup.pl after editing any templates in the template/en/default directory, and after creating or editing any templates in the custom directory. It is required that you run ./checksetup.pl after creating a new template in the custom directory. Failure to do so will raise an incomprehensible error message.

If you are making template changes that you intend on submitting back for inclusion in standard Bugzilla, you should read the relevant sections of the Developers' Guide. The syntax of the Template Toolkit language is beyond the scope of this guide. It's reasonably easy to pick up by looking at the current templates; or, you can read the manual, available on the Template Toolkit home page. One thing you should take particular care about is the need to properly HTML filter data that has been passed into the template. This means that if the data can possibly contain special HTML characters such as <, and the data was not intended to be HTML, they need to be converted to entity form, i.e. &lt;. You use the 'html' filter in the Template Toolkit to do this. If you forget, you may open up your installation to cross-site scripting attacks. Also note that Bugzilla adds a few filters of its own, that are not in standard Template Toolkit. In particular, the 'url_quote' filter can convert characters that are illegal or have special meaning in URLs, such as &, to the encoded form, i.e. %26. This actually encodes most characters (but not the common ones such as letters and numbers and so on), including the HTML-special characters, so there's never a need to HTML filter afterwards. Editing templates is a good way of doing a poor man's custom fields. For example, if you don't use the Status Whiteboard, but want to have a free-form text entry box for Build Identifier, then you can just edit the templates to change the field labels. It's still be called status_whiteboard internally, but your users don't need to know that.

Some CGI's have the ability to use more than one template. For example, buglist.cgi can output itself as RDF, or as two formats of HTML (complex and simple). The mechanism that provides this feature is extensible. Bugzilla can support different types of output, which again can have multiple formats. In order to request a certain type, you can append the &ctype=<contenttype> (such as rdf or html) to the <cginame>.cgi URL. If you would like to retrieve a certain format, you can use the &format=<format> (such as simple or complex) in the URL. To see if a CGI supports multiple output formats and types, grep the CGI for get_format. If it's not present, adding multiple format/type support isn't too hard - see how it's done in other CGIs, e.g. config.cgi. To make a new format template for a CGI which supports this, open a current template for that CGI and take note of the INTERFACE comment (if present.) This comment defines what variables are passed into this template. If there isn't one, I'm afraid you'll have to read the template and the code to find out what information you get. Write your template in whatever markup or text style is appropriate. You now need to decide what content type you want your template served as. The content types are defined in the Bugzilla/Constants.pm file in the contenttypes constant. If your content type is not there, add it. Remember the three- or four-letter tag assigned to your content type. This tag will be part of the template filename. After adding or changing a content type, it's suitable to edit Bugzilla/Constants.pm in order to reflect the changes. Also, the file should be kept up to date after an upgrade if content types have been customized in the past. Save the template as <stubname>-<formatname>.<contenttypetag>.tmpl. Try out the template by calling the CGI as <cginame>.cgi?format=<formatname>&ctype=<type> .

There are a few templates you may be particularly interested in customizing for your installation. index.html.tmpl: This is the Bugzilla front page. global/header.html.tmpl: This defines the header that goes on all Bugzilla pages. The header includes the banner, which is what appears to users and is probably what you want to edit instead. However the header also includes the HTML HEAD section, so you could for example add a stylesheet or META tag by editing the header. global/banner.html.tmpl: This contains the banner, the part of the header that appears at the top of all Bugzilla pages. The default banner is reasonably barren, so you'll probably want to customize this to give your installation a distinctive look and feel. It is recommended you preserve the Bugzilla version number in some form so the version you are running can be determined, and users know what docs to read. global/footer.html.tmpl: This defines the footer that goes on all Bugzilla pages. Editing this is another way to quickly get a distinctive look and feel for your Bugzilla installation. global/variables.none.tmpl: This defines a list of terms that may be changed in order to brand the Bugzilla instance In this way, terms like bugs can be replaced with issues across the whole Bugzilla installation. The name Bugzilla and other words can be customized as well. list/table.html.tmpl: This template controls the appearance of the bug lists created by Bugzilla. Editing this template allows per-column control of the width and title of a column, the maximum display length of each entry, and the wrap behaviour of long entries. For long bug lists, Bugzilla inserts a 'break' every 100 bugs by default; this behaviour is also controlled by this template, and that value can be modified here. bug/create/user-message.html.tmpl: This is a message that appears near the top of the bug reporting page. By modifying this, you can tell your users how they should report bugs. bug/process/midair.html.tmpl: This is the page used if two people submit simultaneous changes to the same bug. The second person to submit their changes will get this page to tell them what the first person did, and ask if they wish to overwrite those changes or go back and revisit the bug. The default title and header on this page read "Mid-air collision detected!" If you work in the aviation industry, or other environment where this might be found offensive (yes, we have true stories of this happening) you'll want to change this to something more appropriate for your environment. bug/create/create.html.tmpl and bug/create/comment.txt.tmpl: You may not wish to go to the effort of creating custom fields in Bugzilla, yet you want to make sure that each bug report contains a number of pieces of important information for which there is not a special field. The bug entry system has been designed in an extensible fashion to enable you to add arbitrary HTML widgets, such as drop-down lists or textboxes, to the bug entry page and have their values appear formatted in the initial comment. A hidden field that indicates the format should be added inside the form in order to make the template functional. Its value should be the suffix of the template filename. For example, if the file is called create-cust.html.tmpl, then <input type="hidden" name="format" value="cust"> should be used inside the form. An example of this is the mozilla.org guided bug submission form. The code for this comes with the Bugzilla distribution as an example for you to copy. It can be found in the files create-guided.html.tmpl and comment-guided.html.tmpl. So to use this feature, create a custom template for enter_bug.cgi. The default template, on which you could base it, is custom/bug/create/create.html.tmpl. Call it create-<formatname>.html.tmpl, and in it, add widgets for each piece of information you'd like collected - such as a build number, or set of steps to reproduce. Then, create a template like custom/bug/create/comment.txt.tmpl, and call it comment-<formatname>.txt.tmpl. This template should reference the form fields you have created using the syntax [% form.<fieldname> %]. When a bug report is submitted, the initial comment attached to the bug report will be formatted according to the layout of this template. For example, if your custom enter_bug template had a field <input type="text" name="buildid" size="30"> and then your comment.txt.tmpl had BuildID: [% form.buildid %] then something like BuildID: 20020303 would appear in the initial comment.

Bugzilla honours the user's Accept: HTTP header. You can install templates in other languages, and Bugzilla will pick the most appropriate according to a priority order defined by you. Many language templates can be obtained from . Instructions for submitting new languages are also available from that location.

This feature should be considered experimental; the Bugzilla code you will be changing is not stable, and could change or move between versions. Be aware that if you make modifications as outlined here, you may have to re-make them or port them if Bugzilla changes internally between versions, and you upgrade. Companies often have rules about which employees, or classes of employees, are allowed to change certain things in the bug system. For example, only the bug's designated QA Contact may be allowed to VERIFY the bug. Bugzilla has been designed to make it easy for you to write your own custom rules to define who is allowed to make what sorts of value transition. By default, assignees, QA owners and users with editbugs privileges can edit all fields of bugs, except group restrictions (unless they are members of the groups they are trying to change). Bug reporters also have the ability to edit some fields, but in a more restrictive manner. Other users, without editbugs privileges, can not edit bugs, except to comment and add themselves to the CC list. For maximum flexibility, customizing this means editing Bugzilla's Perl code. This gives the administrator complete control over exactly who is allowed to do what. The relevant method is called check_can_change_field(), and is found in Bug.pm in your Bugzilla/ directory. If you open that file and search for sub check_can_change_field, you'll find it. This function has been carefully commented to allow you to see exactly how it works, and give you an idea of how to make changes to it. Certain marked sections should not be changed - these are the plumbing which makes the rest of the function work. In between those sections, you'll find snippets of code like: # Allow the assignee to change anything. if ($ownerid eq $whoid) { return 1; } It's fairly obvious what this piece of code does. So, how does one go about changing this function? Well, simple changes can be made just by removing pieces - for example, if you wanted to prevent any user adding a comment to a bug, just remove the lines marked Allow anyone to change comments. If you don't want the Reporter to have any special rights on bugs they have filed, just remove the entire section that deals with the Reporter. More complex customizations are not much harder. Basically, you add a check in the right place in the function, i.e. after all the variables you are using have been set up. So, don't look at $ownerid before $ownerid has been obtained from the database. You can either add a positive check, which returns 1 (allow) if certain conditions are true, or a negative check, which returns 0 (deny.) E.g.: if ($field eq "qacontact") { if (Bugzilla->user->in_group("quality_assurance")) { return 1; } else { return 0; } } This says that only users in the group "quality_assurance" can change the QA Contact field of a bug. Getting more weird: user->email =~ /.*\@example\.com$/)) { if ($oldvalue eq "P1") { return 1; } else { return 0; } }]]> This says that if the user is trying to change the priority field, and their email address is @example.com, they can only do so if the old value of the field was "P1". Not very useful, but illustrative. If you are modifying process_bug.cgi in any way, do not change the code that is bounded by DO_NOT_CHANGE blocks. Doing so could compromise security, or cause your installation to stop working entirely. For a list of possible field names, look at the bugs table in the database. If you need help writing custom rules for your organization, ask in the newsgroup.

Many utilities and applications can integrate with Bugzilla, either on the client- or server-side. None of them are maintained by the Bugzilla community, nor are they tested during our QA tests, so use them at your own risk. They are listed at .