Comparison
Sizzy vs Responsively App
Responsively is a free, open-source app for seeing many devices at once. Sizzy is a paid developer browser that adds project workspaces, isolated sessions, debugging tools, terminals, and coding agents.
Facts checked on 20 October 2026. Feature rows come from each vendor's public docs; pricing comes from each vendor's pricing page.
Short answer
Pick Responsively if you want a free, open-source device previewer and nothing else. Pick Sizzy if you want previews inside a full project workspace with isolated per-device sessions, a console and API client, terminals, and coding agents. Sizzy is $15/month with a 14-day trial; Responsively is free.
What Responsively App documents
Responsively App describes itself as a free and open-source web developer browser. Its public docs list side-by-side device previews, mirrored interactions, Preview Suits for saved device combinations, built-in and custom device profiles, mirrored inspection, screenshots on all devices, hot reload, and an integrated MCP server for MCP-capable coding agents.
What Sizzy documents
Sizzy is a desktop developer browser. Its public feature pages describe project workspaces, synchronized device viewports, one isolated browser session per device, a unified console and REST/GraphQL API client, docked Chromium DevTools, screenshots and screen recording, terminals, and coding agents that use the Claude Code or Codex CLI installed on your machine.
Fit
Where Responsively App fits, and where Sizzy fits
Both tools can be useful. The split below is about the shape of the workflow, not a score.
Responsively App is the better fit when
- Free and open source, with the source available on GitHub.
- Mirrors inspector changes across every device, so a CSS tweak can be checked everywhere at once.
- A built-in MCP server lets MCP-capable coding agents drive the app without a paid plan.
- A browser extension sends the current page from another browser into the app.
Sizzy is the better fit when
- Project workspaces restore the repo path, dev server, tabs, and device layout in one click.
- Each device runs in its own isolated session, so you can stay signed in as a different user per viewport.
- A unified console, an API client for REST and GraphQL, and docked Chromium DevTools sit beside the page.
- Terminals, running processes, and coding agents work in the same window as the previews.
- A paid product with a maintained desktop app, Photo Studio, recording, and a single workspace per project.
Feature table
Sizzy vs Responsively App at a glance
Rows marked "not documented" were not described on the Responsively App pages linked below when we checked on 20 October 2026.
| Feature | Sizzy | Responsively App |
|---|---|---|
| Several viewports side by side | Yes | Yes |
| Synced scrolling, clicks, and typing | Yes | Yes |
| Emulated device presetsResponsively ships built-in profiles and lets you add custom devices. | Yes | Yes |
| Saved device layoutResponsively calls these Preview Suits. | Yes | Yes |
| Separate session per device (cookies and storage) | Yes | Not documented |
| Project workspace with repo path, processes, and restored tabs | Yes | Not documented |
| Unified console across devices | Yes | Not documented |
| Element inspector for each viewportResponsively mirrors the inspector across devices. | Yes | Yes |
| REST and GraphQL API client | Yes | Not documented |
| Screenshots of every device | Yes | Yes |
| Screen recording | Yes | Not documented |
| Integrated terminal | Yes | Not documented |
| Coding agents inside the browserResponsively documents an MCP server for external agents, not an in-app agent chat. | Yes | Partial |
| Accessibility auditsSizzy has no dedicated audit panel; Chromium DevTools includes Lighthouse. | Partial | Not documented |
| Meta and social previews | No | Not documented |
| Open the same preview in another browser or on a phoneResponsively documents a browser extension for sending a page into the app. | No | Not documented |
| macOS, Windows, and Linux | Yes | Yes |
Legend: Yes means the vendor documents it. Partial means it covers part of the workflow. Not documented means it was not described in the pages below, not that it is necessarily missing.
Pricing
What each one costs
Prices are copied from each vendor's own pricing page on the checked date. Never assume they stay the same.
Sizzy
$15/month, $144/year (about $12/month), or $499 once for lifetime access, with a 14-day free trial and no credit card.
Responsively App
Free and open source. The vendor site lists no paid plan; optional support and contributions go through the project's GitHub.
Questions
Questions about Sizzy and Responsively App
Yes. Responsively App describes itself as free and open source, and its public site lists no paid plan. Its source code is on GitHub.
Sizzy adds project workspaces that restore your setup, a separate browser session per device, a unified console and REST/GraphQL API client, Photo Studio and screen recording, terminals with running processes, and in-app coding agents. It is a paid product with a 14-day free trial.
Yes, through a built-in MCP server: MCP-capable coding agents can connect to the app and drive it. Responsively's docs do not describe an in-app agent chat. Sizzy instead runs the Claude Code or Codex CLI you already installed.
Sizzy is $15/month, $144/year (about $12/month), or $499 once for lifetime access. Every plan starts with a 14-day free trial and no credit card.
Sources
Where these facts came from
Checked 20 October 2026. Vendor products change, so confirm on their site before relying on a row.
Keep comparing
The other comparisons
Each page follows the same structure, so you can read the same rows across every vendor.
Overview
All comparison pages
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