September 26, 2011

How To Create QR Codes With Optimal URL Strategies In Mind

(Read in entirety at Search Engine Land. Published 2011)

My last few columns painted a picture of QR codes as a force that will disrupt paid search and organic search marketing strategies. QR codes give consumers a faster, easier shortcut than searching in many situations. I talked about how the generation of these “mobile links” will demand brevity from your SEO’d URLs – but how much?

As with any new field, there is still a lot of mystery about how to engineer QR codes. Today, I’ll explore this point further by looking at the science of QR code creation, how URL size impacts QR size, and how to start engineering a QR-friendly URL strategy.

QR Calculus

Whether your QR marketing happens on business cards, a TV commercial, a catalog spread, a billboard, a website, you’ll eventually run into real estate constraints in your quest to maximize the functional scanning distance of your QR code.

Your goal will become to minimize the use of precious real estate required to display the barcode, yet have the barcode be readable and functional from the farthest possible distance.

For example, a QR code in print need only be scannable from one or two feet away.  A QR code on TV should function from 8 to 10 feet away. If your catalog QR code is functional from five feet away, you’ve needlessly wasted print real estate to boost QR performance.

On the other hand, if a TV QR code requires viewers to get off the couch to scan it from two feet away, you may have saved screen real estate, but at the expense of QR performance (ironically, making your QR a form of wasted real-estate).

So how large is too large? How small is too small? These are questions of optimization.

QR Density, Display & Distance

In QR marketing, the three most important variables are code density, display size and scanning distance.

Here is the basic relationship: the functional scanning distance of a QR is determined by its display size and code density.

If code density increases, and display size does not, functional distance goes down. Conversely, if code density decreases, but display size stays same, functional distance goes up. There’s an inverse relationship between code density and functional distance, given a constant display size.

In other words, QR code density matters; it determines the performance of the other two variables. Higher code density requires more display real-estate to function at the desired distance.

Lower code density requires less real estate to function at the desired distance. Knowing this, you can calculate the optimal QR density and display size required to achieve the functional scanning distance in your QR marketing.


QR Code Optimization

The QR density variable is determined by two inputs: the number of characters you’re encoding multiplied by the error correction settings. This applies regardless of what you’re encoding as a QR code, but we’re focused here on encoding URLs.

The character count of your URLs will vary greatly, based on domain branding, pathway information, keywords used, and tracking parameters. And for each URL size you want to encode, there are four error correction options: 7%, 15%, 25%, and 30%, each of which increase the resulting QR density.

How do you determine which of these settings will produce optimal density, given your URL size?

Sure, your definition of “optimal” will depend on your application: a print QR code may value a higher error correction setting to increase functionality in the event of ink smudging. For screen-based QR displays (TV, online) smudging is a non-issue, so lower error correction settings are valuable.

But that’s all theory. What matters are the trade-offs that happen as you go up and down the density scale. You may be surprised to learn that what you thought was important is far from your optimal choice.

Suppose your URLs are really small, like 14-17 characters. In that case, you should set error correction to the lowest value of 7%.

Why? The resulting QR would be 21×21 code – the smallest achievable. But if you encode that same small URL using the highest error correction setting (30%), you’d get a 29×29 code instead.

Big deal? Consider how much more area is contained in a 29×29 code than a 21×21: it’s not just 8 x 8. Dust off the ol’ distributive property from algebra, and you’ll see the 29×29 in fact covers nearly twice as much area as a 21×21 (841 units vs 441 units).

That means, when displayed at the same size, a 29×29 QR code will only have about half the functional distance of a 21×21. Conversely, the scanning distance you gain by using a 21×21 is 90% greater than using a 29×29.

If you have limited real estate to devote to the QR code, which of these settings is optimal? More than likely, the 21×21 QR.

On the other hand, if your URLs are 18-24 characters in length, the lowest density you can achieve is a 25×25 whether your error correction is set to 7% or 15%. The highest setting produces a 29×29 once again.

In this case, your optimal choice is likely the higher 15% setting, because you can’t get any smaller, and you maximize error correction. Similar trade-offs can be considered around your URL domain, pathway, keywords, and parameter size.

Interestingly, social URL shortener tools like and URL lengths fall in this range. encodes their 20-character URLs using the optimal lower error correction settings, as evidenced by their 25×25 QR output. encodes their 19 character URLs at the highest setting, as evidenced by their 29×29 QR output. (This is actually suboptimal, since a lower density 25×25 is achievable at the lower settings, and would increase functional scanning distance by 35%.)

QR optimization is new territory for most of us – and it’s nearly impossible to guess such results. There are few QR tools that allow you to modify QR error correction settings to discover your optimal QR density.

If you need help predicting which error correction settings and URL sizes will create a given QR density, check out our handy Guide to Creating Optimal QR Codes at the Pure Oxygen blog.

Years ago, most websites were designed without any SEO requirements in mind. This increased the total costs of ownership and missed opportunity. There is a similar opportunity now to future-proof your URL strategies by integrating QR optimal requirements.

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