How to set Checkbox with post request?

If it's a boolean field, the JSON data for the particular field should look like this:

field_mark_as_discounted: { und: [ { value: 1 } ] }

This doesn't appear to be working. I am trying the following:

field_character_type: {und: [{value: 0}]}

With no luck

I can check a checkbox but I cannot uncheck a checkbox.

IIRC, to uncheck a boolean, you may have to send null. Try some of these:

field_character_type: null

field_character_type: {und: null}

field_character_type: {und: [null]}

field_character_type: {und: [{value: null}]}

Things may also change if your field is required or not, so perhaps try toggling the required bit on the field instance settings to see if that changes how things behave.

Marking fixed because #6 looks correct and haven't heard from hby01.

After much trial and error to uncheck the checkbox the only one that works is

field_character_type: {und: null}

I would have assumed it to be:

field_character_type: {und: [{value: "0"}]}
or
field_character_type: {und: [{value: false}]}

If you want to check the checkbox you can pretty much send anything other than {und: null}. For sanity I send this:

field_character_type: {und: [{value: true}]}