The Brownie GUI

Brownie includes a GUI for viewing test coverage data and analyzing the compiled bytecode of your contracts.

Parts of this section assume a level of familiarity with EVM bytecode. If you are looking to learn more about the subject, Alejandro Santander from OpenZeppelin has written an excellent guide - Deconstructing a Solidity Contract.

Getting Started

To open the GUI, run the following command from within your project folder:

$ brownie gui

Or from the console:

>>> Gui()

Once loaded, the first thing you’ll want to do is choose a contract to view. To do this, click on the drop-down list in the upper right that says “Select a Contract”. You will see a list of every deployable contract within your project.

Once selected, the contract source code is displayed in the main window with a list of opcodes and program counters on the right. If the contract inherits from more than one source file, tabs will be available to switch between sources. For example, in the image below the Token contract includes both Token.sol and SafeMath.sol:

The Brownie GUI

Working with Opcodes

Mapping Opcodes to Source

Highlighting a section of code will also highlight the instructions that are associated with it. Similarly, selecting on an instruction will highlight the related source.

Click the Scope button in the top left (or the S key) to filter the list of instructions such that only those contained within the highlighted source are shown.


Opcodes displayed with a dark background are not mapped to any source, or are mapped to the source of the entire contract. These are typically the result of compiler optimization or part of the initial function selector.

Mapping Opcodes to Source

Jump Instructions

Click the Console button in the top left (or the C key) to expand the console. It shows more detailed information about the highlighted instruction.

  • When you select a JUMP or JUMPI instruction, the console includes a “Target:” field that gives the program counter for the related JUMPDEST, where possible. The related JUMPDEST is also highlighted in green. Press the J key to show the instruction.
  • When you select a JUMPDEST instruction, the console includes a “Jumps:” field that gives a list of program counters that point at the highlighted instruction. Each related JUMP/JUMPI is also highlighted in green.
Jump Instructions


  • Right clicking on an instruction will apply a yellow highlight to all instructions of the same opcode type.
  • Press the R key to toggle highlight on all REVERT opcodes.

Viewing Coverage Data

For an in-depth look at your test coverage, click on the drop-down list in the upper right that says “Select Report” and choose “coverage”. A new drop-down list will appear where you can select which type of coverage data to view (branches or statements).

Relevant code will be highlighted in different colors:

  • Green code was executed during the tests
  • Yellow branch code executed, but only evaluated truthfully
  • Orange branch code executed, but only evaluated falsely
  • Red code did not execute during the tests
Viewing Coverage Data

Viewing Security Report Data

Once the brownie analyze command has finished, the GUI will show a new security report. Select the security report and the MythX report type. If any vulnerabilities have been found, they will be highlighted based on their severity:

  • Green Low severity (best practice violations)
  • Yellow Medium severity (potential vulnerability), needs to be fixed
  • Red High severity (critical, immediate danger of exploitation)

The report data can also be directly accessed in reports/security.json.

Security Report GUI

Report JSON Format

Project coverage data is saved to reports/coverage.json using Brownie’s standard report format. Third party tools wishing to display information in the Brownie GUI can also save JSON files within the reports/ folder.

Brownie expects JSON reports to use the following structure:

    "highlights": {
        // this name is shown in the report type drop-down menu
        "<Report Type>": {
            "ContractName": {
                "path/to/sourceFile.sol": [
                    // start offset, stop offset, color, optional message
                    [123, 440, "green", ""],
                    [502, 510, "red", ""],
    "sha1": {} // optional, not yet implemented

The final item in each highlight offset is an optional message to be displayed. If included, the text given here will be shown in the GUI console when the user hovers the mouse over the highlight. To not show a message, set it to "" or null.