Voiden API Client: Open Source Alternative to Postman

Voiden API Client is an open-source, offline-first API client for developers who want to design, test, document, and version API requests directly in Git.

It is often used as an alternative to Postman, Insomnia, Bruno, and HTTPie by teams that want Markdown-based API specs, local files, no cloud lock-in, no required accounts, and a Git-native workflow.

What is Voiden API Client?

Voiden is a desktop API client built around plain Markdown files. Instead of storing API collections in a proprietary cloud workspace or exported JSON files, Voiden keeps requests, documentation, environments, and context in .void files that can be committed alongside your code.

This makes Voiden useful for developers and teams that want API documentation and API testing to live in the same repository as the product.

Voiden is especially useful for:

• backend developers
• API-first teams
• teams replacing Postman
• teams wanting Git-native API collections
• developers who prefer local-first tools
• open-source projects documenting APIs
• teams avoiding cloud sync and vendor lock-in
• developers who want API requests and docs in Markdown

Key features

Git-native API workflow

• Store API requests in plain Markdown .void files
• Commit API collections alongside your code
• Review API changes in pull requests
• Branch, diff, and merge API specs with Git
• Keep requests, docs, headers, auth, and context together
• Avoid proprietary collection formats and cloud sync

API testing and documentation

• Build and test HTTP requests
• Document endpoints next to runnable requests
• Link requests like code blocks
• Reuse request blocks for headers, auth, params, and context
• Comment on JSON and XML responses inline
• Preview rich responses including PDFs and videos
• Publish static API documentation with Cast

Local-first developer experience

• Works offline by default
• No required account
• No required cloud workspace
• No telemetry-first workflow
• Electron desktop app for macOS, Windows, and Linux
• Themes and scripting support
• Plugin SDK for extensions

Voiden API Client vs Postman

Feature	Voiden API Client	Postman
Main use case	Git-native, offline-first API client and API documentation	Managed API collaboration and testing platform
License	Apache-2.0	Proprietary
Deployment	Local desktop app	Managed cloud SaaS with desktop app
Storage	Markdown .void files in your repository	Cloud workspaces and proprietary collection formats
Offline use	Core product focus	Available, but cloud collaboration is central
Collaboration	Git-based collaboration through commits and pull requests	Team workspaces, sharing, roles, and cloud sync
Documentation	Markdown-based API docs and static publishing	Managed API documentation and portals
Data control	High, because files stay local or in your Git repository	Data is managed through Postman’s platform
Best for	Developers wanting local files, Git workflows, and no cloud lock-in	Teams wanting managed collaboration, workspaces, and enterprise features
Cost model	Free open-source software	Subscription-based SaaS pricing

Choose Voiden API Client if you want an open-source Postman alternative with local files, Markdown specs, Git-native collaboration, and no required cloud account.

Choose Postman if you want a mature managed API platform with cloud workspaces, collaboration features, enterprise controls, and a larger ecosystem.

Voiden API Client vs Insomnia

Voiden and Insomnia are both developer-friendly API clients, but they have different priorities.

Insomnia is a mature API client focused on request testing, collections, environments, GraphQL, and developer workflows. Voiden is more focused on Git-native API specs, Markdown files, offline-first usage, and keeping API documentation close to the codebase.

Feature	Voiden API Client	Insomnia
Main use case	Git-native API client and Markdown API docs	API testing and design client
Storage	Plain Markdown .void files	Project and collection-based workspace
Offline workflow	Core focus	Supported
Documentation	Markdown-first and static publishing	API design and documentation workflows
Best for	Teams wanting API specs in Git	Developers wanting a polished API client

Voiden API Client vs Bruno

Bruno is one of the closest alternatives to Voiden because both products focus on local-first API collections and Git-friendly workflows.

Bruno stores API collections as plain text files and is a strong Postman alternative for teams that want Git-based collaboration. Voiden is more Markdown-native and focuses on combining API requests, documentation, and context in .void files.

Feature	Voiden API Client	Bruno
Main use case	Markdown-based API client and documentation	Git-friendly API client
File format	.void Markdown files	Plain text collection files
Git workflow	Core product focus	Core product focus
Documentation	Strong Markdown documentation workflow	Request collections and API testing
Best for	Teams wanting API docs and requests together	Teams wanting local API collections in Git

Voiden API Client vs HTTPie

HTTPie is a command-line HTTP client and API testing tool. Voiden is a desktop API client with Markdown documentation, reusable request blocks, response previews, and static publishing.

Choose HTTPie if you want a fast CLI tool for making HTTP requests.

Choose Voiden if you want a visual desktop API client with Git-native documentation and reusable API specs.

At a glance

Attribute	Details
License	Apache-2.0
Category	Developer Tools / API Client
Main users	Backend developers, API teams, open-source maintainers
Focus	API testing, Markdown API specs, Git-native workflows
Deployment	Local desktop app
Cloud	None required
Offline	Yes
Format	Markdown .void files
Stack	TypeScript, Electron, React
Alternatives	Postman, Insomnia, Bruno, HTTPie

Getting started

Voiden can be used as a local desktop app for API testing and documentation.

For local development from source:

git clone https://github.com/VoidenHQ/voiden.git
cd voiden
yarn install
yarn workspace @voiden/core-extensions build
cd apps/electron
yarn start