MDN ha un formato standard di tabelle di compatibilità per la nostra documentazione web open; in altre parole, la documentazione di tecnologie come DOM, HTML, CSS, JavaScript, SVG, ecc., che viene condivisa attraverso tutti i browsers. Questo articolo spiega come usare le nostre funzionalità per aggiungere dati di compatibilità alle pagine MDN.

Come accedere alla repository dati

I dati sono conservati in un repository GitHub — vedi https://github.com/mdn/browser-compat-data. Per accedervi, hai bisogno di un account GitHub, fare un fork del repository browser-compat-data attraverso il tuo account, infine clonare il fork localmente sulla tua macchina.

Choosing a feature to add data for

First of all, find a feature that you want to add browser-compat-data for. This could be an HTML element, CSS property, JS language feature or JS API interface, for example. We would like to encourage you to work on API features, as we already have people working on HTML, JS, and CSS. You can find the status of features that need their data adding to the repo on our Browser Compat Data migration spreadsheet.

Preparing to add the data

Before adding some new data, you should make sure that your fork is up-to-date with the main repo (it contains the same content), create a new branch inside your fork to contain your additions, then pull that branch into your local clone so you can start working inside it:

Adding the main browser-compat-data repo as a remote

Go to your local clone of your fork in your terminal/command line, and add a remote pointing to the main (upstream) repo like so (you only need to do this once):

If you are unsure whether you've done this, you can check what remotes your repo has using

Updating your fork with the remote's content

Creating a new branch to do your work in

Next, go to your remote fork (it will be at https://github.com/your-username/browser-compat-data) and create a new branch to store your changes for this data addition. This can be done by:

For example, if you were wanting to add data for the WebVR API, you'd create a branch called something like "webvr".

Switching to the new branch

At this point, go back to your terminal/command line, and update your fork's local clone to include your new branch using the following command:

Adding the data

To add the data, you need to create a new file or files to store your compat data in. The files you need to create differ, depending on what technology you are working on:

Each file you create has to follow the pattern defined in the schema contained within our repo; you can see the detailed schema description here.

Basic compat data structure

Let's look at an example. CSS property JSON files for example need the following basic structure:

You have the css object, inside of which is a properties object. Inside the properties object, you need one member for each of the specific features you want to define the compat data for. Each of these members has a __compat member, inside of which the actual data goes.

In HTML, CSS, and JS pages, you'll normally only need one feature. API interfaces work slightly differently — they always have multiple sub-features (see {{anch("Sub-features")}}, below).

Basic structure inside a feature

Inside a feature __compat member, you need to include the following members:

mdn_url: Contains the URL of the reference page for this feature on MDN. Note that this needs to be written without the locale directory inside, e.g. /docs/... not /docs/en-US/... (or whatever). This is added in by the macro when the data is put on the page, for localization purposes.
support: Contains members representing the browser support information for this feature in all the different browsers we want to report.
status: Contains members reporting the standards track status of this feature.

The names of the browser members are defined in the schema (see Browser identifiers). You should use the full list of currently defined identifiers. If you wish to add another browser, talk to us first, as this could have a wide-ranging impact and should not be done without careful thought.

In a basic browser compat data file, you'll only need to include "version_added" inside the browser identifier members (we'll cover {{anch("Advanced cases")}} later on). The different values you might want to include are as follows:

A version number: If you know the exact version in which a browser started to support your feature, use a string representing the number, e.g. "47".
true: If a browser supports a feature but you don't know the exact version number, use the value true. This equivalent to the \{{CompatVersionUnknown}} macro call in the old manual tables.
false: If a browser does not support a feature, use the value false. This is equivalent to the the \{{CompatNo}} macro call in the old manual tables.
null: If you don't know whether a browser supports a feature or not, use the value null. This is equivalent to the \{{CompatUnknown}} macro call in the old manual tables.

Inside the status member, you'll include three submembers:

"experimental": This should be set to true if the feature is experimental, or false otherwise.
"standard_track": This should be set to true if a feature is on some kind of standards track (most commonly W3C/WHATWG, but there are also other standards efforts such as Khronos, TC39, etc.) or false otherwise.
"deprecated": This should be set to true if the feature is deprecated, or false otherwise.

The feature data for border-width (also see border-width.json) is shown below as an example:

"__compat": {
  "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/border-width",
  "support": {
    "chrome": {
      "version_added": "1"
    },
    "webview_android": {
      "version_added": "2"
    },
    "edge": {
      "version_added": true
    },
    "edge_mobile": {
      "version_added": true
    },
    "firefox": {
      "version_added": "1"
    },
    "firefox_android": {
      "version_added": "1"
    },
    "ie": {
      "version_added": "4"
    },
    "ie_mobile": {
      "version_added": "6"
    },
    "opera": {
      "version_added": "3.5"
    },
    "opera_android": {
      "version_added": "11"
    },
    "safari": {
      "version_added": "1"
    },
    "safari_ios": {
      "version_added": "3"
    }
  },
  "status": {
    "experimental": false,
    "standard_track": true,
    "deprecated": false
  }
}

Adding a description

There is a fourth, optional, member that can go inside the __compat member — description. This can be used to include a human-readable description of the feature. You should only include this if it is hard to see what the feature is from glancing at the data. For example, it might not be that obvious what a constructor is from looking at the data structure, so you can include a description like so:

{
  "api": {
    "AbortController": {
      "__compat": {
        ...
      },
      "AbortController": {
        "__compat": {
          "mdn_url": "https://developer.mozilla.org/docs/Web/API/AbortController/AbortController",
          "description": "<code>AbortController()</code> constructor",
          "support": {
            ...
          }
        }
      }

      ... etc.
    }
  }
}

Sub-features

In a page where the compat table has more than one row, you'll need multiple subfeatures inside each feature to define the information for each row. This can happen, for example, when you've got the basic support for a feature stored in one row, but then the feature also has a new property or value type that was addded much later in the specification's life and is only supported in a couple of browsers.

As an example, see the compat data and corresponding MDN page for the background-color property. The basic support exists inside the __compat object as explained above, then you have an additional row for browsers' support for "alpha channel for hex values", which contains its own __compat object.

{
  "css": {
    "properties": {
      "background-color": {
        "__compat": {
          ...
        },
        "alpha_ch_for_hex": {
          "__compat": {
            ...
          },
        }
      }
    }
  }
}

For an API, you've got the top two levels defined as api.name-of-the-interface, then a top-level __compat section to define the overall browser compatibility of the interface, then a sub-feature for each of the methods, properties, and constructors contained inside the interface. The basic structure looks like this:

{
  "api": {
    "VRDisplay": {
      "__compat": {
        ...
      },
      "cancelAnimationFrame": {
        "__compat": {
          ...
        }
      },
      "capabilities": {
        "__compat": {
          ...
        }
      },

      ... etc.

    }
  }
}

See VRDisplay.json for a full example.

Adding data: Advanced cases

There are some advanced features that you'll want to include in browser compat data. The aim of this section is to list the most common ones, providing an example of each to show how you can implement them in your own compat data.

Including a footnote

Often compat tables will include footnotes related to certain entries that explain useful details or strange behavior that developers will find useful. As an example, the Chrome Android entry for {{domxref("VRDisplay.capabilities")}} (see also VRDisplay.json) (at the time of writing) had a footnote "Currently supported only by Google Daydream." To include this in the capabilities data, we added a "notes" submember inside the relevant "chrome_android" submember; it would look like this:

Including a vendor prefix

If a feature is supported behind a vendor prefix in one or more browsers, you'll want to make that clear in the browser compat data. imagine you had a feature that was supported with a -moz- prefix in Firefox. To specify this in the compat data, you'd need to add a "prefix" submember inside the relevant "firefox" submember. It would look something like this:

Including browser preferences or flags

Some features may be supported in a browser, but they are experimental and turned off by default. If a user wants to play with this feature they need to turn it on using a preference/flag.

To represent this in the compat data, you need to add the "flags" submember inside the relevant browser identifier submember. The value of "flags" is an array of objects each of which contains of three members:

So to add a preference/flag to the Chrome support for a feature, you'd do something like this:

If a feature is behind two or more flags, you can add additional objects to the "flags" array, like in this case, for example:

Including a version where support was removed

Sometimes a feature will be added in a certain browser version, but then removed again as the feature is deprecated. This can be easily represented using the "version_removed" submember, which takes as its value a string representing the version number it was removed on. For example:

Including multiple support points for the same browser entry

Sometimes you'll want to add multiple support data points for the same browser inside the same feature.

As an example, the {{cssxref("text-align-last")}} property (see also text-align-last.json) was added to Chrome in version 35, supported behind a pref.

The support mentioned above was then removed in version 47; also in version 47, support was added for text-align-last enabled by default.

To include both of these data points, you can make the value of the "chrome" submember an array containing two support information objects, rather than just a single support information object:

Including an alternative name

Occasionally browsers will support a feature under a different name to the name defined in its specification. This might be for example because a browser added experimental support for a feature early, and then the name changed before the spec stabilized.

To include such a case in the browser compat data, you can include a support information point that specifies the alternative name inside an "alternative_name" member.

Let's look at an example. The {{cssxref("border-top-right-radius")}} property (see also border-top-right-radius.json) was supported in Firefox:

Pushing a change back to the main repo

Once you are finished with adding your compat data, you should first test it using the following commands:

If it is looking OK, you then need to commit it and push it back up to your remote fork on GitHub. You can do this easily with terminal commands like this:

Now go to your remote fork (i.e. https://github.com/your-username/browser-compat-data) and you should see information about your push at the top of the files list (under "Your recently pushed branches"). You can create a pull request (starting the process of pushing this to the main repo) by pressing the "Compare & pull request" button, then following the simple prompts on the subsequent screen.

At this point, you just need to wait. A reviewer will review your pull request, and merge it with the main repo, OR request that you make changes. If changes are needed, make the changes and submit again until the PR is accepted.

Inserting the data into MDN pages

Once your new data has been included in the main repo, you can start dynamically generating browser compat tables based on that data on MDN pages using the \{{Compat}} macro. This takes a single parameter, the dot notation required to walk down the JSON data and find the object representing the feature you want to generate the compat table for.

Above the macro call, to help other contributors finding their way, you should add a hidden text that is only visible in MDN contributors in edit mode:

As an example, on the {{httpheader("Accept-Charset")}} HTTP header page, the macro call looks like this: \{{Compat("http.headers.Accept-Charset")}}. If you look at the accept-charset.json file in the repo, you'll see how this is reflected in the JSON data.

As another example, The compat table for the {{domxref("VRDisplay.capabilities")}} property is generated using \{{Compat("api.VRDisplay.capabilities")}}. The macro call generates the following table (and corresponding set of notes):