Nodes store every message for every account. To keep that bounded and to make spam cost something, each account pays rent for its storage. It is a yearly fee, not a fee per post.
How it works#
- An account rents storage units from the StorageRegistry contract on OP Mainnet. The price is set in US dollars and paid in ETH. A unit lasts one year.
- Each unit adds a fixed number of slots per kind of message: casts, reactions, links, profile fields, verifications and username proofs.
- An account needs at least one unit before the network accepts its messages. Signing up through an app usually includes one.
When it fills up#
Nothing breaks. When an account goes over its limit for a kind, the node drops that kind's oldest message to make room. A new cast pushes out the oldest cast. This is called pruning.
For a timeline that's usually fine. It is less fine for follows, since pruning a very old follow silently unfollows someone. People who want to keep more can rent more units.
Deleted casts leave a tombstone that still takes a slot until it is pushed out.
When it expires#
If an account lets all its storage expire, it has a 30-day grace period to renew. After that it can lose its messages.
Reading it from the node#
The exact slots per unit have changed over time, and the node tracks units by the year they were bought. Ask the node rather than hard-coding numbers:
curl -s "$NODE/v1/storageLimitsByFid?fid=3"{"limits": [
{"name": "CASTS", "limit": 108000, "used": 51340, ...},
{"name": "LINKS", "limit": 54000, "used": 4660, ...},
{"name": "REACTIONS", "limit": 54000, "used": 53162, ...},
{"name": "USER_DATA", "limit": 1500, "used": 10, ...},
...
],
"units": 30,
"unitDetails": [{"unitType": "UnitTypeLegacy", "unitSize": 16},
{"unitType": "UnitType2024", "unitSize": 14},
{"unitType": "UnitType2025", "unitSize": 0}]}When we checked, dwr had 30 units and was close to the reaction limit. Past it, each new like pushes out an old one.
What this means for readers#
A node holds what is currently stored, not everything that was ever posted. If an old cast is missing, it may have been pruned, deleted, or signed by a key that was later removed. Archive what you need yourself.