Plug.Parsers accepts a length: key with a value of approximate bytes to accept and can be used in an endpoint file.
# endpoint.ex
plug Plug.Parsers,
pasrsers: [:urlencoded, :multipart],
length: 100_000_000 # 100 MB body size (approximately)
You can also configure the length for a specific parser:
plug Plug.Parsers,
parsers: [:urlencoded, {:multipart, length: 100_000_000}] # 100 MB body size (approximately)