HTTP/2 lets browsers fetch a page's files over one connection at the same time, which helps pages with many images and scripts. Browsers use it only over HTTPS, and only where the host's servers support it.

A queue behind every page

A web page is not one file. A typical small business home page is assembled from dozens: the page itself, style sheets, scripts, fonts, a logo, photographs and icons.

Under HTTP/1.1, the version of the web's basic protocol most sites still use, a browser fetches those files over a handful of connections, one file at a time on each. The rest wait their turn.

HTTP/2, finished as a standard last year, removes the queue. The browser opens one connection and asks for everything at once, and the server sends the files back side by side as they are ready.

Current browsers already support it. Whether your visitors get it depends on your host.

Which browsers use it

The last is the reassuring one. Switching HTTP/2 on breaks nothing, because a browser that cannot use it never asks for it.

The fourth matters to offices still on Windows 7, where Internet Explorer 11 keeps using the old protocol. Those visitors get the site exactly as they do today.

Why it comes with HTTPS

The standard allows HTTP/2 without encryption, but every major browser chose to use it only over HTTPS. A site on plain HTTP does not get it at all.

That gives sites still on HTTP one more reason to move. A certificate for your own domain is no longer expensive, and once installed it covers every page and file.

It also answers an old complaint, that HTTPS makes a site slower. Setting up an encrypted connection takes a moment, and HTTP/2 needs one connection where HTTP/1.1 opened several.

On a page with many files, the secure version can now be the quicker one.

What it changes for a small site

The gain depends on the page. Pages with many small files gain most: a gallery of thumbnails, a menu with a photograph of every dish, a shop category showing forty products.

A page made of a few large files gains little. If the home page is slow because of one enormous photograph, HTTP/2 will not save it; the photograph still has to arrive.

Nor does it fix a slow server. If the host takes a second or two to build each page, that delay comes before any of the files are requested.

Some old speed tricks matter less now, such as spreading files across extra domain names to get more connections. Under HTTP/2 that can even slow things down, since each extra domain needs a connection of its own.

How to tell whether you have it

Open the site in Chrome and open the developer tools at the Network panel. Right-click a column heading, turn on Protocol, and reload the page.

Files delivered over HTTP/2 show h2 in that column; the rest show http/1.1. Check an HTTPS address, since a plain HTTP one will show the old protocol regardless.

Files from other services, such as web fonts, maps and analytics, come from their own servers with their own answers. The line that matters is the page itself and the files from your own domain.

A worked example

A Hong Kong-style cafe in a busy suburban plaza has a menu as long as the boards on its walls: breakfast sets, baked rice, noodles, milk tea, pineapple buns.

Its website shows every item with a small photograph, nearly a hundred on one page.

On phones, the page arrived in stages. Headings appeared first, then the photographs filled in a row at a time over several seconds.

A test on WebPageTest showed why. The waterfall chart, which draws each file as a bar on a timeline, formed a long staircase: six images at a time, each batch waiting for the last.

The site was on plain HTTP, on a server whose software was older than HTTP/2.

The host moved the account to a newer server with HTTP/2 switched on, and the site moved to HTTPS with a certificate for its own domain.

The photographs were also resized to the boxes they fill, rather than arriving at full camera size.

In the next test the staircase was gone. The image requests started together on one connection, and the menu filled in as a page rather than row by row.

Questions for your host

Is HTTP/2 supported on the server my site is on, and is it switched on for my account? If not, is there a plan or a server where it is, and what does moving involve?

Which web server software runs the site, and which version? The two programs that run most hosting servers added HTTP/2 only in the second half of last year, so an older server cannot offer it.

And if the site uses a content delivery network, which serves copies of files from servers near each visitor, does that support it too?

A sign of how current the servers are

HTTP/2 on its own is not a reason to change hosts. It is one sign of how current a host's servers are.

A host running web server software from several years ago may also be behind on PHP versions and security fixes, which matter more. If the answer to the HTTP/2 question is no, ask what else is old.

The counter-case

For a site of a few pages with few files, the difference may be hard to notice. Oversized images and a slow server usually cost more, and fixing them comes first.

A site that cannot move to HTTPS yet, because something on it only works over plain HTTP, gets nothing from HTTP/2 until it can. That move is the real project.

Otherwise the advice is simple: get HTTPS on your own domain, ask the host whether HTTP/2 is on, and let it do its work.

HTTPS before HTTP/2

  1. Check that the site uses HTTPS everywhere.
  2. Get a certificate for your own domain.
  3. Look for h2 in Chrome's developer tools.
  4. Ask the host whether HTTP/2 is switched on.
  5. Resize oversized images while you are at it.
  6. Stop adding extra domains for speed.
  7. Test the slowest pages again afterwards.

Step four decides it. HTTP/2 is a feature of the server, not something a site can switch on from the inside, so the host's answer is the whole question.

Why the certificate should carry your own domain rather than the host's is covered in shared SSL that shows the host's name.

Frequently asked questions

What is HTTP/2 in plain terms?

A newer version of the protocol browsers use to fetch web pages. It lets a browser request all of a page's files at once over one connection instead of queueing them.

Do visitors need anything special to use it?

No. Current versions of Chrome, Firefox, Safari and Edge support it, and older browsers simply carry on with HTTP/1.1, so switching it on breaks nothing.

Why does HTTP/2 need HTTPS?

The standard allows it without encryption, but every major browser chose to use it only over HTTPS. A site on plain HTTP does not get it at all.

Which pages gain the most from it?

Pages with many small files, such as galleries, illustrated menus and shop categories. Pages slowed by one huge image or a slow server gain little until those are fixed.

How can I tell if my site uses it?

Open Chrome's developer tools at the Network panel, add the Protocol column and reload the page. Files sent over HTTP/2 show h2; the rest show http/1.1.

Which questions should go to the host?

Whether HTTP/2 is supported and switched on for your account, which web server version runs your site, and, if not, which plan or server offers it.

West Coast Media Solutions Inc. provides web design, web development, hosting, digital marketing, and business consulting to organisations across Canada, drawing on more than twenty-five years in the field.

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