I’ve been trying to figure out why Google Maps’s city labels seem much more readable than those of other mapping sites.

For instance, here’s the same area on Google Maps and Bing Maps. Notice how Google’s city labels seem easier to read and less cluttered than Bing’s:

And here’s the same area on Google Maps and Yahoo! Maps. Notice how Google’s city labels also seem much easier to read:

Whenever you’re scanning Google Maps, the label you’re searching for seems to stand out just a little sooner than on Yahoo! or Bing.

But why?

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At first I assumed Google Maps was easier to read because it had fewer labels than the other sites. But this isn’t the case.

For instance, counting all of the city dot icons appearing entirely within the image below, Google displays 86 cities:

Bing, meanwhile, labels 91 cities—just five more than Google:

And Yahoo! actually labels fewer cities than Bing and Google—just 83:

So there’s not much of a difference.

If Google’s superior readability isn’t on account of fewer labels, then what else explains it? If you look closely at Google Maps, Google seems to employ a number of unique effects...

1. THICK, WHITE OUTLINES (THAT OBSCURE ALL BACKGROUND DATA)

I can see you thinking it now: “Wait, doesn’t Yahoo! Maps also have white outlines around the text of its city labels?” Yahoo! certainly does—but there’s a key difference: Google’s outlines are thicker, and you can’t see the map’s background details (e.g., roads, rivers, etc.) behind them.

For instance, look here at Google’s “New York” label. Notice how you can’t see any roads or other details behind the “N”, the “e”, or any of the other letters:

 Now look at Yahoo!’s “New York” label:

Yahoo!’s outlines are much thinner, causing the text to be interrupted by dark road lines and water details. This forces readers to give a second look to many labels—and instead of reading Yahoo!’s labels, you’re often deciphering them.

But look what happens if we enlarge Yahoo!’s outlines to resemble Google’s:

The map becomes much easier to read with the Google-style, enlarged outlines (especially around New York).

2. A GREATER NUMBER OF LABEL SIZES

In addition to the thicker outlines, Google also uses more city label sizes/classes than the other sites. For instance, Google uses four city label classes on the map below:

But Bing uses only three:

And so does Yahoo!:

Google’s use of an additional label class allows smaller cities to fade into the background. This causes larger cities (often used as reference points) to stand out much more, making everything easier to find.

3. MORE LABEL COLORS

In addition to using more text sizes than the other sites, Google also uses more label colors. This allows larger cities to stand out because the smaller cities (with their lighter labels) disappear into background.

Notice how much lighter Google’s fourth label class is, compared to its other label classes:

The effect of these lighter labels may not seem that drastic—but look what happens when we make Bing look a little more like Google by giving it a fourth class of lighter and smaller city labels:

The map instantly becomes less cluttered, and all without removing any of its detail. In fact, by adding a fourth class of labels, we’ve arguably added even more detail to the map.

And zooming in, the changes are even more dramatic:

As you can see, Google’s use of a fourth label class is part of the reason why Google’s map looks much less cluttered than the others.

Thicker outlines. More label classes. Lighter text. If all that wasn’t enough, Google seems to use at least a few more tricks...

CITY DONUTS

I’ve often noticed that Google labels more cities on its map of Iowa than on its map of Illinois, and while this doesn’t happen on every zoom-level, it happens on quite a few.

For instance, here on Google’s seventh zoom-level, 68 Iowa cities are shown, while only 41 Illinois cities are shown:

This is odd given that Illinois is both larger than Iowa (in terms of land area) and has many more cities than Iowa:

In trying to make sense of this, I noticed that Iowa is uniformly covered with cities, while Illinois is not: central Illinois is uniformly covered with cities, but the areas immediately outside Chicago and St. Louis are relatively devoid of cities.

And when I looked at metros in other states, I noticed that they also had relatively fewer cities around them. In other words, nearly every major U.S. metro area has a ring of white space immediately around it on Google Maps.

A few examples:

ATLANTA

MINNEAPOLIS / ST. PAUL

ST. LOUIS

Interesting, isn’t it?

These white space rings outside of major cities are even more apparent when you remove everything else from the map using Google Maps API 3:

ST. LOUIS

ATLANTA

DALLAS / FORT WORTH

By removing cities immediately outside of major metro areas, Google is making these metro areas stand out even more. This, in turn, makes it easier to browse the map because major cities are often used as reference points.

Moreover, the removal of cities immediately outside of large metro areas also makes the map look less cluttered.

Speaking of clutter, Google also seems to deliberately avoid clustering cities too closely together. For instance, take a closer look at Google’s overall city distribution, compared to Bing’s:

Bing clusters cities together, especially close to Washington, Baltimore, Philadelphia, and throughout Connecticut. Google, meanwhile, leaves more space between cities, giving them room to breathe—and making its map easier to read overall.