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I'm looking for a plugin that can check the current opened file and instantly tell me whether it is valid JSON or not (eg whether there's a comma or a bracket missing) — is there any? I'm currently using JSONView on Chrome but it's a pain to always go check the file in the browser and back.

I'm often writing data in json by hand, hence why I feel this could save me a lot of time.

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Not a plugin for Notepad++ but XML ValidatorBuddy is also a JSON editor and comes with a built-in JSON syntax checker and auto-completion. It is a standalone Windows tool. – Clemens Oct 23 '12 at 9:38

You might be able to use a JSON formatter to accomplish the task (since it would likely complain or do something wrong -- say, like indent improperly -- if the JSON's invalid). See Is there an extension to reindent JSON in Notepad++?. Similarly, there's a JSONViewer Notepad++ plugin the might help in the same way.

Another less-than-ideal alternative would be to just use one of the online JSON validators.

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+1 for JSON Viewer- I use it all the time. can also format/reindent your JSON string. Only thing is you have to manually use the functionality- I don't think you can do it every time a .json file is opened – Robotnik Jul 9 '12 at 0:16
Thanks, I upvoted, but it's still not quite what I hoped for; JSMin ignores errors, and JSON Viewer while it does fail if the json is not properly formatted, I still get much more if I parse it using JSONView in Google Chrome since as opposed to JSON Viewer it tells exactly what is missing and where. Oh well. I suppose I can only hope someday somebody able to code npp plugins comes across this and implements a simple one-button solution to parse and validate json. – Mahn Jul 9 '12 at 16:26
@Mahn: Thanks. Necessity is the mother of invention, so perhaps you should be that someone... – martineau Jul 9 '12 at 16:54
I'd love to, but I'm involved in a somewhat big project atm and time is ticking out :) maybe someday. – Mahn Jul 9 '12 at 19:56
It's worth noting that the JSONView Chrome extension does a great job but crashes on significantly large files (can't get it to process a 90meg file... not sure what it's limit is though). – Sean Colombo Feb 18 at 17:04

There is plugin for NPP+ called JSLint. It is a plugin to validate JavaScript-code, but it works also just fine with JSON-files.

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