Keep push payloads short and safe on a lock screen

How to do it

Push text shows on lock screens and smart watches, and passes through the platform's servers. Apple's guidelines (4.5.4) say not to send sensitive personal data by push. Write "A new message from your clinic", not the message. Send an ID and let the app fetch the details over its own API. APNs and FCM limit a standard payload to 4,096 bytes. Web push services accept 4,096 bytes after encryption, which leaves 3,993 bytes for your JSON. The same idea for email is send only what the message needs.

Example

const MAX_PAYLOAD_BYTES = 3993;
const SENSITIVE = /\b\d{6}\b|\b\d{4}[ -]?\d{4}[ -]?\d{4}[ -]?\d{4}\b|[$€£]\s?\d/;

test.each(Object.keys(PUSH_TEMPLATES))('%s is safe on a lock screen', type => {
  const payload = JSON.stringify(renderPush(type, SAMPLE_DATA[type]));
  expect(payload).not.toMatch(SENSITIVE);
  expect(Buffer.byteLength(payload)).toBeLessThanOrEqual(MAX_PAYLOAD_BYTES);
});

import json
import re
import pytest

MAX_PAYLOAD_BYTES = 3993
SENSITIVE = re.compile(r"\b\d{6}\b|\b\d{4}[ -]?\d{4}[ -]?\d{4}[ -]?\d{4}\b|[$€£]\s?\d")

@pytest.mark.parametrize("kind", PUSH_TEMPLATES)
def test_push_is_safe_on_lock_screen(kind):
    payload = json.dumps(render_push(kind, SAMPLE_DATA[kind]))
    assert not SENSITIVE.search(payload)
    assert len(payload.encode()) <= MAX_PAYLOAD_BYTES

How to check

A unit test renders every push template with sample data and fails if the text holds a sign-in code, an amount or a card number. It also fails if the JSON is over 3,993 bytes.