Personally, I prefer using online tools for performing quick manipulation on different data formats like JSON, XML, CSV and so on. They’re platform independent and always within reach of my hand (since I mainly work in a browser). After we published an article about 7 best JSON viewers, I was told about Knowledge Walls, a similar service containing many tools for text data manipulation.

As a JSON viewer, Knowledge Walls offers a good amount of useful features like expanding children by levels, search by levels, different colors for different type of data, and some others:
KW JSON Viewer

Also, it has plenty of different tools for data manipulation. For example, if you’ve got a one-line JSON string which is inconvenient to analyze, you can format the JSON string nicely:
Format JSON

Or vice versa, you can minimize a JSON string:
Minimize JSON

If you have a CSV file with a delimiter that is not appropriate (it happens when a comma character is already used as a decimal point in some locales), you can quickly change the delimiter:

CSV Delimiter Convertor

Well, to make a long story short, the service offers many other tools (even working with HTML, JavaScript and CSS) that you can evaluate for yourself.

Basically, this service is very useful in many cases, but there are still some tools that could be made better. For example the XML validation tool looks inconvenient to me since it doesn’t highlight the errors in the source XML, forcing me to read the error description. It would be good at least to show a snippet where the error took place as W3C Markup Validator does.