diff --git a/01.md b/01.md
index 2ff81ebf..9258d2f7 100644
--- a/01.md
+++ b/01.md
@@ -30,7 +30,7 @@ The only object type that exists is the `event`, which has the following format
 }
 ```
 
-To obtain the `event.id`, we `sha256` the serialized event. The serialization is done over the UTF-8 JSON-serialized string (with no white space or line breaks) of the following structure:
+To obtain the `event.id`, we `sha256` the serialized event. The serialization is done over the UTF-8 JSON-serialized string (which is described below) of the following structure:
 
 ```json
 [
@@ -43,6 +43,14 @@ To obtain the `event.id`, we `sha256` the serialized event. The serialization is
 ]
 ```
 
+To prevent implementation differences from creating a different event ID for the same event, the following rules MUST be followed while serializing:
+- No whitespace, line breaks or other unnecessary formatting should be included in the output JSON.
+- No characters except the following should be escaped, and instead should be included verbatim:
+  - The line break, `0x0A`, as `\n`
+  - A double quote, `0x22`, as `\"`
+  - A backspace, `0x5C`, as `\\`
+- UTF-8 should be used for encoding.
+
 ## Communication between clients and relays
 
 Relays expose a websocket endpoint to which clients can connect.