When researching browser-based proxies, you will meet both Holy Unblocker and Ultraviolet. They are closely related but not the same thing. Holy Unblocker LTS was a web proxy project that brought together a website interface, server-side services and several proxy technologies, and its development continued as InvisiProxy LTS (see Holy Unblocker vs InvisiProxy). Ultraviolet is a proxy engine originally developed by TitaniumNetwork that uses service workers to intercept and process browser requests.
The confusion exists because Holy Unblocker has used Ultraviolet as one of its proxy options. The newer InvisiProxy LTS also includes Scramjet, which its current website recommends as the primary option, with Ultraviolet as a fallback.
What Is Holy Unblocker?
Holy Unblocker was a browser-based web proxy that let users reach supported websites through a web interface, with no traditional desktop proxy app. It combined a user-facing interface with components for processing requests, managing browser-side functionality and talking to proxy services. Depending on the version, those included Ultraviolet, Scramjet, Rammerhead and supporting transport technologies.
Because development continued as InvisiProxy LTS, older Holy Unblocker documentation and newer InvisiProxy documentation may describe different versions, configurations or recommendations.
- A browser-based interface for supported websites
- Integration with engines such as Ultraviolet and Scramjet, depending on version
- Supporting services and transport options
- Configuration options for self-hosting and deployment
- Compatibility that varies by engine, browser and destination site
Holy Unblocker is a broader proxy project, not simply another name for Ultraviolet.
What Is Ultraviolet?
Ultraviolet is an open-source proxy engine from TitaniumNetwork. It processes website requests inside a controlled browser environment using a service worker, a browser feature that can intercept certain network requests for a site. It uses this to rewrite website resources so supported content works through its proxy. It also supports configurable URL encoding, request processing and integration with supporting transports, though compatibility is not universal.
- An open-source proxy engine
- Service-worker-based request interception
- Integration with supporting libraries and transport components
- A codebase developers can study and adapt under its license
Maintenance matters. The official Ultraviolet repository states that the project is no longer actively maintained as it once was and names Scramjet as its successor. It remains useful as a reference for existing installations, but check the latest repository information before choosing it for a new deployment.
Quick Comparison
| Feature | Holy Unblocker / InvisiProxy LTS | Ultraviolet |
|---|---|---|
| Type | Complete web proxy project | Proxy engine |
| Main purpose | Provides a web interface and integrates proxy components | Processes supported website requests through a browser-based proxy |
| User interface | Includes a website interface | Usually supplied by a separate application |
| Service workers | Depends on the integrated engine and version | Uses service workers |
| Other engines | May integrate several | One specific engine |
| Self-hosting | Deploy the overall project | Integrate into a compatible application |
| Configuration | Application-level and engine-specific settings | Engine-specific settings and supporting components |
| Maintenance | Depends on the current InvisiProxy LTS release | Repository names Scramjet as its successor |
| Best use case | An integrated proxy project | Maintaining or studying an Ultraviolet-based setup |
The key difference is scope: Holy Unblocker is the overall application, while Ultraviolet is one of the technologies that can power a proxy application. They are not direct substitutes in every situation.
1. Architecture
Holy Unblocker combined a user-facing website with server-side services, browser-side code and proxy engines. A request typically meant the user entering an address, the application using an engine, and the engine processing the needed resources (see how Holy Unblocker works). Exact architecture varies by version, so older installs may differ from current InvisiProxy LTS releases.
Ultraviolet focuses on the proxying itself. Its service worker intercepts supported browser requests and processes them. The application that integrates it supplies the interface, serves the assets, configures supporting services and makes the parts work together. That separation lets developers use Ultraviolet in different applications.
To use a ready-made project, the complete application structure matters. To build your own, an engine may offer more flexibility, though you must integrate and maintain it. Neither approach guarantees better performance or compatibility, since those depend on the implementation and the sites involved.
2. Features
It helps to separate what the application provides from what its engine provides.
- Holy Unblocker lineage has included, depending on release: a browser interface with an address or search input, access to different engines, settings for choosing between them, supporting transports, server-side configuration, and extra browsing or privacy options in some versions. Not every feature exists in every release (see Holy Unblocker features).
- Ultraviolet focuses on request interception, URL rewriting and encoding, configurable behavior and integration with compatible components.
As a complete application, Holy Unblocker may offer more user-facing functionality, while Ultraviolet is narrower by design. Counting features without considering their roles would be misleading.
3. Performance
There is no universal answer. Performance depends on the engine, server, network, browser and destination site, and an app built on Ultraviolet may perform differently from one using Scramjet. Key factors:
- Server resources: CPU, memory and throughput (see server requirements).
- Network latency: distance between user, proxy and destination.
- Website complexity: many scripts, images and API calls take longer to process.
- Transport configuration: it affects both compatibility and speed.
- Browser support: service workers and storage behave differently across browsers.
- Destination restrictions: sites may limit automated requests or reject certain server addresses.
To compare fairly, test the same destination sites with the same browser, server resources and network, and measure load times, errors and resource use over repeated runs. Don't assume an engine is always faster because it works better on one site. InvisiProxy LTS recommends Scramjet first and keeps Ultraviolet as a fallback, which is useful context but doesn't prove every Scramjet deployment outperforms every Ultraviolet one.
4. Website Compatibility
A proxy may load a basic page and still fail on sites that depend on complex JavaScript, real-time communication, authentication flows or strict security controls.
- Ultraviolet was designed to support a range of popular sites, but results vary by site and implementation. Older versions may hit problems already fixed elsewhere in the ecosystem.
- Holy Unblocker's compatibility depends on the selected engine and configuration. Multiple engines give alternatives when one struggles, but don't guarantee every site works. A site might load its homepage and still fail on video, sign-in or an interactive app.
Common causes of failure are covered in why websites don't work:
- Unsupported or complex JavaScript behavior
- WebSocket or other real-time connection problems
- Authentication and CAPTCHA challenges
- Browser-specific restrictions
- Missing or misconfigured proxy services
- Changes made by the destination website, or restrictions on the host network
The right fix depends on the actual failure. Switching engines may help in some cases but cannot resolve every server-side restriction. See common problems and fixes.
5. Security and Privacy
Neither should be assumed completely private or anonymous. Security depends on the software version, server configuration, browser, connection security and the trustworthiness of whoever runs the service.
- Holy Unblocker: self-hosting gives the operator control over configuration and maintenance, and with it responsibility for securing the server, updating dependencies, protecting admin access and monitoring activity. On a third-party instance, consider whether the operator is trustworthy and how they handle browsing data.
- Ultraviolet: being open source lets developers inspect its code and dependencies, but that doesn't make every installation secure. Its maintenance status also matters, so review the repository, dependencies and available fixes before using an existing install in a new public deployment.
No browser-based proxy guarantees anonymity, prevents all tracking or eliminates data exposure. HTTPS protects data in transit to the HTTPS endpoint, but doesn't make an operator trustworthy, and cookies, account activity and fingerprinting still matter. Avoid entering sensitive information into an unfamiliar public proxy. For more context, read Holy Unblocker vs VPN and our disclaimer.
6. Self-Hosting
The easier option depends on whether you want a complete application or an engine to integrate into your own project.
- Holy Unblocker or InvisiProxy LTS: you obtain the right source version, install compatible dependencies, configure the server and make sure the included components work together, often with a domain, HTTPS and a reverse proxy. The process differs between older Holy Unblocker releases and current InvisiProxy LTS, so follow the instructions for your version. See How to Self-Host Holy Unblocker.
- Ultraviolet: it can be integrated into a compatible web application but isn't a complete deployment alone. Its official repository points developers to Ultraviolet-App for a complete, customizable setup. Expect to need a compatible runtime, package dependencies, static asset serving, a service-worker setup and a supporting transport service, and to check existing installs for outdated dependencies and version mismatches.
A maintained, complete application can be easier for beginners because it supplies more of the surrounding infrastructure, while an individual engine suits developers who want to customize and understand internals. A complete application isn't automatically easier if its documentation is outdated or its parts need heavy manual configuration. Once installed, see how to configure Holy Unblocker.
7. Maintenance and Future Development
The official Ultraviolet repository says the project has been superseded by Scramjet and is no longer maintained as actively as before. It remains available for existing deployments and for developers who need to study or maintain the engine. InvisiProxy LTS has continued to evolve, recommending Scramjet as primary and offering Ultraviolet as a fallback.
That doesn't mean every Ultraviolet installation must be removed immediately. An established deployment may still meet its needs if its operator understands the maintenance risks and keeps the surrounding system secure. Before starting a new project, examine:
- The current release and repository activity
- The maintenance status of dependencies
- Browser compatibility and known issues
- The license and distribution requirements
- Available documentation and upgrade instructions
- Whether the engine fits your intended workload
If you already run an Ultraviolet-based app, evaluate your requirements before changing engines, because migration may touch dependencies, configuration, transports and application code. Avoid combining incompatible package versions or copying configuration from unrelated releases.
8. Where Does Scramjet Fit In?
Scramjet is relevant because it is named as Ultraviolet's successor. Both process requests through a browser-based proxy environment but are separate implementations with different codebases and maintenance histories. Scramjet's documentation presents it as an interception-based proxy designed with performance, security and developer maintainability in mind, and InvisiProxy LTS recommends it first, with Ultraviolet as an alternative when a site works better there.
Should you switch? Not necessarily in every case. For a new project, start with the successor's current documentation. For an existing one, first check compatibility, dependencies and the migration effort. A site that works through Ultraviolet may behave differently through Scramjet, so test the sites and features your users need before changing production. For a focused comparison, see Holy Unblocker vs Scramjet.
9. Pros and Cons of Holy Unblocker
Advantages
- A complete website interface, not only an engine
- Can combine multiple proxy technologies, depending on version
- A starting point for people interested in self-hosting
- A broader structure for settings and supporting services
- A development lineage that continued as InvisiProxy LTS
Limitations
- Requirements and features vary by version
- Hosting and maintenance need technical knowledge
- Compatibility isn't guaranteed for every website
- Public instances raise trust and privacy questions
- Older installations need careful review before continued use
10. Pros and Cons of Ultraviolet
Advantages
- An open-source proxy engine
- Uses service workers to process supported requests
- Can be integrated into a compatible application
- A codebase for studying browser-based proxy architecture
- Has been used by projects such as Holy Unblocker LTS
Limitations
- Not a complete website or hosting solution by itself
- Compatibility varies between websites and implementations
- Its official repository names Scramjet as its successor
- Existing deployments may need dependency and maintenance review
- Integration needs compatible supporting components
11. Which One Should You Choose?
- A complete Holy Unblocker / InvisiProxy LTS deployment if you want an integrated application with an interface and supporting components. Check the documentation for your exact release first.
- Ultraviolet if you need to maintain an existing Ultraviolet-based application, study its architecture, or integrate it into a compatible project where its limitations are understood.
- Scramjet for a new implementation if you want to follow the direction InvisiProxy LTS recommends. Test the sites you need and review the latest documentation first.
Choose on requirements rather than labels. Compatibility, maintenance, security and ease of deployment are better criteria than assuming one option is universally superior.
Frequently Asked Questions
Is Holy Unblocker the same as Ultraviolet?
No. Holy Unblocker is a broader web proxy project, while Ultraviolet is a proxy engine. Holy Unblocker LTS used Ultraviolet as one of its available technologies.
Does Holy Unblocker use Ultraviolet?
Holy Unblocker LTS included it. The current InvisiProxy LTS project, which continues that lineage, offers both Scramjet and Ultraviolet, with Scramjet recommended as primary.
Is Ultraviolet still maintained?
Its official repository says it is no longer actively maintained in the same way and has been superseded by Scramjet. Check the repository for the latest code, releases and maintenance status before deploying it.
Is Ultraviolet better than Holy Unblocker?
They serve different roles, so a direct winner isn't meaningful in every situation. Holy Unblocker is a complete project, while Ultraviolet is an engine that can be integrated into an application.
Is Ultraviolet faster than Scramjet?
It depends on the implementation, configuration, browser, server and destination site. No engine is guaranteed to always be faster.
Can I use Ultraviolet without Holy Unblocker?
Yes. It can be integrated into a compatible web application, and the official repository points developers to Ultraviolet-App for a complete application setup.
Does Ultraviolet work on mobile browsers?
That depends on the browser's support for the needed features, the application setup and the site being accessed. Test your intended mobile browsers rather than assuming universal compatibility.
Is Holy Unblocker safer than Ultraviolet?
Neither can be declared safer in every situation. Security depends on the implementation, maintenance, configuration and the trustworthiness of the operator.
Can I replace Ultraviolet with Scramjet?
Possibly, but it isn't always a drop-in replacement. Review the current documentation and dependencies, then test your required sites and features before changing a production deployment.
Where can I find the Ultraviolet source code?
The official repository is at github.com/titaniumnetwork-dev/Ultraviolet. Review its README, license and maintenance notes before using the code.
Conclusion
Holy Unblocker and Ultraviolet are closely connected but play different roles. Holy Unblocker is a broader application that can integrate multiple components, while Ultraviolet is a specific engine built on service-worker request interception. Ultraviolet remains relevant for understanding existing deployments, but its repository names Scramjet as its successor, and InvisiProxy LTS recommends Scramjet first while keeping Ultraviolet as a fallback.
For users, the best choice depends on the sites they need to support. For developers, compatibility, maintenance, security and correct configuration matter most. Understanding the distinction makes it easier to evaluate proxy technologies without confusing a complete application with one of the engines that powers it.