Is everything stored on-chain forever?

No. Block headers and commitments persist permanently, but transaction data can be pruned. Post-Fusaka, blob data is designed to be temporary (kept for ~18 days). Full nodes prune old data. Archive nodes maintain historical data for those who need it. Specialized DA networks also ensure this data remains accessible.

Why did my rollup fees drop so much in 2024-2025?

Two major upgrades: EIP-4844 (March 2024) introduced blob storage, making data posting 90-95% cheaper than calldata. Fusaka (December 2025) added PeerDAS, enabling up to 8x more blob capacity per block while reducing validator bandwidth by 85%. Combined, these upgrades dropped Layer 2 transaction fees from $5-10 to $0.10-0.50.

Are NFT images really stored "on the blockchain"?

Usually no. Most NFTs store only a hash or URI on-chain. This points to the actual image stored on IPFS, Arweave, or centralized servers. The on-chain data proves ownership and links to the media. Exception: Some collections, like Bitcoin Ordinals, inscribe media directly into blockchain witness data. This process makes them truly on-chain but much more expensive.

What's the difference between L1 calldata, blobs, and external DA layers?

L1 Calldata: Permanent storage on Ethereum, highest cost, maximum security. Blobs: Temporary storage (18 days), 95% cheaper than calldata, sufficient for rollup fraud proofs. External DA (Celestia, EigenDA): Specialized networks, 100-8,000x cheaper than L1, additional trust assumptions. Most rollups now use blobs as the sweet spot between cost and security.

Who keeps historical blockchain data after nodes prune it?

There are multiple parties involved. These include block explorers like Etherscan and Blockchair, and analytics firms such as Dune and Nansen. Archive node operators are also involved, along with DA networks for rollup data. Finally, community archivists play a role. If you need guaranteed access to specific historical data, run your own archive node or use archival services. The blockchain's commitment structure ensures anyone can verify data authenticity even if they retrieve it from a third party.

How does PeerDAS work without sacrificing security?

PeerDAS uses data availability sampling and erasure coding . Each validator randomly samples small portions of blob data from different peers. Through statistical properties, if enough validators successfully sample their random portions, you can be confident. This ensures that the complete data is available. Erasure coding means the data can be reconstructed even if some portions are missing. This provides the same security guarantees as full downloads but with 85% less bandwidth.

What happens if a rollup stops posting data to Ethereum?

Users can exit to Layer 1 using the data that was previously posted. For optimistic rollups, there's a 7-day challenge window. During this time, anyone can submit fraudulent documents if data is missing or incorrect. For ZK rollups, the validity proofs ensure only correct state transitions are accepted. If data stops being posted, new transactions stop. However, existing user funds remain secure. They are withdrawable based on the last valid state.

Can blockchain data be deleted or edited?

No, blockchain data is immutable once finalized. You cannot delete or edit past blocks without breaking the cryptographic chain, which would be immediately detected by all nodes. However, you can decide what data to put on-chain initially. This is the hashes or full data. Nodes can prune old transaction data locally. They keep enough information to verify the chain's integ

Is everything on-chain forever?

No. Headers and commitments persist, but many payloads (like blobs) are designed to be temporary. Nodes prune; archives and DA networks keep the bulk data accessible.

Why did rollup fees drop?

Because of blobs and better DA plumbing. Posting data got cheaper and cleaner, so users pay less.

Are Ordinals/NFT media really on-chain?

Sometimes. Ordinals write media into witness data (on-chain). Many NFT ecosystems keep media off-chain with an on-chain hash to guarantee integrity.

Who keeps historical files?

Explorers, analytics firms, DA/archival networks (IPFS/Arweave), and communities. If you care about durability, pin or archive your own copies too.

Blockchain Data Storage- The Complete Guide To How Data Actually Works In 2026