---
title: Regex Efficiency
description: Considerations around writing efficient regex
---
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# Regex Efficiency
## Considerations around writing efficient regex
A few ideas to keep in mind when writing regex. [Please see Using Regular Expressions (regex) in SiteSpect](https://doc.sitespect.com/knowledge/using-regular-expressions-in-sitespect?hsLang=en) first if you have not already.
### Use Character Classes instead of Lazy wilds when possible
Let's say you have
```
some content
```
and you want to capture the classe(s), the following negated character class is more efficient
```
]*>[^<]+
```
which will be more efficient than using the lazy wilds. A negated character class works well when you know a single character that you want to match up until.
### Don't use Lazy when the last possible match is more than halfway to the end
This comes into play when you want to match from a patter in the source of the page that is at the top such as
```
```
all the way to the bottom such as
```
```
in that case you would want to use a greedy regex to reduce unnecessary backtracking.
```
(.*)
```
If you used a .\*? it would work but cause additional backtracking.
#### How do I see and compare my regex performance in SiteSpect?
[Enable comprehensive debugging information](https://doc.sitespect.com/knowledge/enable-comprehensive-debugging-information?hsLang=en) to see the number of milliseconds it takes for each Variation to run while in a [Preview Session](https://doc.sitespect.com/knowledge/previewing-campaign-components-1?hsLang=en).
#### What other tools can help?
[External regex tools](https://doc.sitespect.com/knowledge/regular-expressions-tips-for-sitespect?hsLang=en)
#### Other interesting reading
[https://www.loggly.com/blog/five-invaluable-techniques-to-improve-regex-performance/](https://www.loggly.com/blog/five-invaluable-techniques-to-improve-regex-performance/)
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