Neat Nest is not in the list when I tap a file
Some apps send JSON files as an unknown type. Open Neat Nest and use Open a file instead, or Share the file to Neat Nest.
Another app keeps opening my JSON files
Neat Nest's home screen names that app. Open its app info, tap Open by default, then Clear defaults. Next time, pick Neat Nest and Always.
It says the file is read only here
The app that handed over the file did not allow writing to it. Save makes a copy where you pick. Opening the file with Open a file instead usually allows saving back.
The Tree view says the document is not valid JSON
Go to the Text view; the status bar shows the line and column of the first problem. Tap it to jump there. Common ones are a comma before } or ], single quotes, and comments, which JSON does not allow.
A warning says a number may be rounded
Numbers over 9007199254740991, or with more than 17 digits, cannot be kept exactly by many other apps and languages. Neat Nest keeps them as written; the warning is for whatever reads the file next.
Copy says the text is too big for the clipboard
Android's clipboard holds about a megabyte. Use Share or Save as for bigger text.
Does Neat Nest send my files anywhere?
No. It has no internet access at all. See the privacy policy.