Inspect blocks and sync status with basectl

Read a single Base block, check how far your node is behind the network, and stream Flashblocks as JSON using basectl.

Use these commands to look at chain data and confirm your node is keeping up with the network.

basectl block

Fetches a single L2 block and prints it either as an easy-to-read table (default) or as full JSON (--json). Short alias: b.

<REF> can be any of the following:

• A block number in decimal (for example 42417649)
• A block number in hex (for example 0x2871c71)
• A tag: latest, safe, finalized, or earliest
• A 32-byte block hash

Looking up a block by hash works even for blocks that are no longer on the canonical chain, such as orphaned or reorged-out blocks. The pending tag is not supported.

Flag	Description
--json	Print JSON with values decoded for you (decimal numbers, readable timestamps, and context fields for the network and the block you asked for).
--raw	Add to --json to print the block exactly as the node returns it (hex values, original field names). This matches the output of cast block --json. Using --raw without --json is an error.

The default table converts hex values to decimal and Unix timestamps to YYYY-MM-DD HH:MM:SS UTC. With --json, timestamps come back as an object with unix, utc, and local fields so you don’t have to do any timezone math.

Inspect a block

# Inspect the latest block on Sepolia
basectl -c sepolia block latest

# Decimal and hex block numbers give the same result
basectl -c sepolia block 42417649
basectl -c sepolia block 0x2871c71

# JSON output pipes cleanly into jq
basectl -c mainnet block --json finalized | jq '{number, hash, gasUsed, baseFeePerGas}'

# Use the short alias `b`
basectl -c mainnet b latest

# Look up a block by hash (works for orphaned or reorged-out blocks too)
basectl -c sepolia block 0x9fa0d82dfdf395d552e92caec6a9d5482c53f1800e8f3ff29994b7a431447148

basectl sync-status

Shows how far your node is behind the network. It reads the sync status from both the consensus layer (CL) and the execution layer (EL), and compares your node’s head against a public endpoint. Each request runs in parallel; if either the CL or EL request fails, the command stops early, and the public comparison is skipped if the public endpoint is unreachable.

The CL response lists every L1 and L2 head the node knows about, each with a block number, hash, and timestamp. With --json, the output also includes a precomputed safe-head lag (safeLagSeconds and safeLagBlocks, the difference between the unsafe and safe heads) so you don’t have to calculate it yourself.

When the EL is still syncing, the output adds processedBlocks (how many blocks it has caught up so far) and remainingBlocks (how many are left), so you can see the size of the gap instead of just “syncing: true”.

A tip_reference row compares your node’s head against the network’s public endpoint and reports one of:

• caught_up — within the tolerance set by --tip-tolerance (default 5 blocks)
• behind — further behind than the tolerance
• ahead — ahead of the public endpoint
• unavailable — the public endpoint couldn’t be reached

Flag	Description
--el-rpc <URL>	Use a specific execution-layer RPC URL instead of the one in your config.
--cl-rpc <URL>	Use a specific consensus-node RPC URL instead of the one in your config.
--tip-tolerance <BLOCKS>	How many blocks your node can be behind and still count as caught_up. Default 5 (about 10 seconds at Base’s 2-second block time). Use 0 for strict alerting, or a larger number to reduce noise.
--json	Print JSON with decoded values and the extra fields described above.
--raw	Add to --json to print the raw sync-status response. Using --raw without --json is an error.

Check sync status

# Check sync status on a devnet
basectl -c devnet sync-status

# Check sync status on a local Sepolia node
basectl -c sepolia sync-status

# JSON output includes the precomputed safe-head lag
basectl -c sepolia sync-status --json | jq '{safeLagSeconds, safeLagBlocks, elActivelySyncing}'

basectl flashblocks

Streams live Flashblocks to your terminal as one JSON object per line. For an interactive view instead, use basectl monitor flashblocks.

Stream Flashblocks as JSON

# Stream Flashblocks on Sepolia
basectl -c sepolia flashblocks

To learn more about Flashblocks and 200ms preconfirmations, see the Flashblocks FAQ.

Related

• basectl overview
• Diagnose node health
• Interactive dashboard