Read logs and failures
Begin with “Events, topics and logs” and work toward “Receipt and error challenge set”. Each available lesson includes a visual explanation and a quick knowledge check.
Read in order or choose a topic below. Completion marks stay in this browser. All 20 lessons in this track are available.
- 01
Events, topics and logs
Read the structured notes that contracts leave during execution.
7 MIN READ - 02
Understand why a call reverted
Separate error bytes from the underlying reason execution failed.
7 MIN READ - 03
Compute an event signature hash
Topic zero usually identifies the event’s canonical shape.
4 MIN READ - 04
Indexed versus non-indexed arguments
The declaration decides which values become topics.
4 MIN READ - 05
Decode an ERC-20 Transfer event
Read two indexed addresses and one raw amount.
4 MIN READ - 06
Decode an Approval event
An allowance record describes spending permission.
4 MIN READ - 07
Anonymous events explained
An anonymous event omits the signature topic.
4 MIN READ - 08
Indexed strings and hashed topics
An indexed string topic is a digest, not recoverable text.
4 MIN READ - 09
Logs inside a receipt
A receipt places surviving log records in transaction context.
4 MIN READ - 10
Why reverted logs do not persist
Rollback removes logs from the reverted execution scope.
4 MIN READ - 11
Event ordering in nested calls
Nested execution can interleave logs from different emitters.
4 MIN READ - 12
Decode Error(string)
A common revert format carries a dynamic message.
4 MIN READ - 13
Decode Panic(uint256)
A panic carries a numeric code instead of a free-form string.
4 MIN READ - 14
Read arithmetic panic codes
Different runtime failures can use different numeric categories.
4 MIN READ - 15
Decode a custom Solidity error
The error declaration supplies names and types for its payload.
4 MIN READ - 16
Empty revert data explained
A failed call can return no diagnostic bytes at all.
4 MIN READ - 17
Errors can be bubbled up
A caller can pass a child’s failure bytes onward.
4 MIN READ - 18
Why revert bytes can be spoofed
Recognizing an error format does not authenticate its author.
4 MIN READ - 19
Link an error to a call frame
Find the first failing frame and the callers that handled it.
4 MIN READ - 20
Receipt and error challenge set
Combine event decoding, rollback and failure context.
4 MIN READ