puter.kv.MAX_VALUE_SIZE The largest value the key-value store accepts, in bytes.
It's 408576 (399 KB). A value is measured as the UTF-8 bytes of JSON.stringify(value), so a string's quotes and escapes count.
puter.kv.MAX_VALUE_SIZE
<html>
<body>
<script src="https://js.puter.com/v2/"></script>
<script>
puter.print("Max Value Size: " + puter.kv.MAX_VALUE_SIZE);
</script>
</body>
</html>