The operation
What the pipe to JSON array converter computes
Four operations, applied in a fixed order, with no configuration exposed. The input is split on the pipe character. Each resulting piece is trimmed of leading and trailing whitespace. Any piece that is now the empty string is discarded. What survives is serialised as a JSON array with a two-space indent.
That order matters more than it looks. Trimming happens before the emptiness test, so a field of three spaces and a field of zero characters are indistinguishable by the time the test runs, and both are removed.
The whole computation happens in the page. There is no request, therefore no server-side allowance to spend and no imposed length ceiling.