Sleipnir (神马浏览器) is a highly-customisable, multi-window (MDI) web browser that fuses the Trident (IE) and Gecko (Firefox) engines into one interface. Born in Japan and nick-named after Odin’s eight-legged horse, it targets power-users who want Opera-style mouse gestures, Chrome-level speed and Firefox-class extensibility—yet still keep the classic menus and toolbars they grew up with.
What sets it apart
- Dual-engine – switch between IE (Trident) and Gecko on a per-tab basis for maximum site compatibility.
- Super-charged gestures – draw a trail with the right button to change tabs, close windows, scroll or run user scripts; built-in editor lets you assign any menu command or external program to a new gesture.
- XML-driven interface – every menu, button and toolbar is stored as editable XML, so you can literally re-arrange the entire UI without an add-on.
- RoboForm-ready – plug-in adapter lets you use RoboForm, KeePass or other password managers natively.
- SmartSearch & incremental find – highlight any word, drag up/down and choose “Wiki”, “Translate”, “Color-mark”, “Copy text line”, etc.
- Tab-group colours – assign a colour folder to news, work, social tabs; collapse or move whole groups at once.
- Favorites Editor (FvEditor) – add per-site flags: disable images, block ActiveX, mute sounds, force IE-engine—perfect for old intranet pages.
- Script & plug-in API – write UserJS, VBScript or full DLL extensions; stock plug-ins include RSS reader, weather, QR generator.
- Cross-platform – Windows desktop (XP→11), macOS, iOS/iPadOS and Android share bookmarks via Fenrir Pass or local Wi-Fi sync.
Quick look at performance
Portable package ≈ 80 MB; with 20 tabs open RAM sits around 450 MB on Windows 11—roughly half of current Chromium-based rivals. Cold-start time (SSD) is under 1 s; engine switch (Gecko ↔ Trident) reloads the tab in ~200 ms.
Typical use-cases
- Enterprise: keep legacy IE-only intranet apps in Trident tabs while browsing the modern web in Gecko tabs—no separate browser needed.
- Research: colour-code tabs by project, use drag-and-gesture to send selected text to custom search engines or external tools.
- Privacy: disable third-party cookies, turn off auto-phoning updates, run UserJS to strip tracking pixels.
- Automation: fire external batch files or PowerShell scripts straight from a gesture or toolbar button.
How to get started
- Download the multilingual installer from the official site or reputable mirrors .
- Choose “Custom” to make it portable (writes settings to program folder).
- Run the First-Run Wizard—pick gesture style (Opera or Sleipnir), decide which engine new tabs default to.
- Right-click any toolbar → “Customize” to drag buttons, menus or address bars wherever you want.
- Visit Options → Advanced → Scripts & Plug-ins to import UserJS or download community extensions.
Bottom line
If you miss deep UI customisation, mouse gestures and the ability to toggle rendering engines on the fly, Sleipnir is the swiss-army knife you’ve been looking for—lightweight, free and still actively maintained .