• Why UK Businesses Are Looking at Open Source HR Software

• The Main Open Source HR Platforms Worth Evaluating

  • Horilla HRM

  • OrangeHRM

  • Odoo HR Module

  • Sentrifugo

  • Factorial (Freemium, Not Fully Open Source)

• Horilla vs OrangeHRM: The Core Comparison

  • Feature Completeness

  • UK Compliance Readiness

  • Implementation Effort

  • UI and Staff Adoption

  • Long-Term Maintenance

• What "Open Source" Actually Costs in Practice

• When Horilla Makes Sense for a UK Business

• When Odoo HR Makes More Sense

• The Implementation Question Most Buyers Underestimate

• A Note on AI-Assisted HR Workflows

• Making the Decision

• Frequently Asked Questions

If you are searching for open source HR software in the UK, the core appeal is straightforward: no per-seat licensing fees, full access to the source code, and the freedom to adapt the system to your processes rather than the other way around. What is less obvious is which platform actually delivers on that promise for a UK business — and what the real cost of ownership looks like once implementation, compliance requirements, and ongoing support enter the picture.

This article compares the leading options, with particular attention to Horilla HRM, and explains what UK businesses should weigh before committing.

Why UK Businesses Are Looking at Open Source HR Software

The HR software market is crowded with SaaS platforms charging per employee per month. At 30 staff, that model is manageable. At 150, the invoices become significant. At 500, it is a board-level conversation.

Open source shifts the cost structure. You pay for implementation, hosting, and support rather than perpetual licensing. The trade-off is that you take on more responsibility for configuration, maintenance, and upgrades. Whether that makes sense depends entirely on your internal capability and how much customisation you actually need.

For UK businesses specifically, there are additional considerations. GDPR compliance, UK payroll legislation, statutory leave entitlements, and IR35 contractor rules all create requirements that not every open source platform handles well out of the box. A system built for a US or Indian market may need significant custom development before it is fit for a UK employment context.

The Main Open Source HR Platforms Worth Evaluating

Horilla HRM

Horilla is a Python-based, open source HRM platform covering recruitment, onboarding, attendance, leave management, payroll, performance appraisal, and asset management. It is actively maintained, with a public repository and a commercial support tier for businesses that want implementation assistance rather than self-service setup.

The platform is modular. You can deploy only the modules relevant to your business without activating the full suite. For a 50-person company that primarily needs leave management, attendance tracking, and a basic employee directory, that modularity keeps the system lean.

Horilla's UI is cleaner than most open source alternatives — which matters when non-technical HR staff are using it daily. The learning curve is real but not steep.

From a UK compliance standpoint, Horilla supports configurable leave policies, so statutory entitlements under UK employment law can be mapped in. Payroll configuration requires attention during setup to align with HMRC requirements, but in most cases this is a configuration task rather than a development task.

The honest limitation: Horilla is not plug-and-play. A business without technical resource will need implementation support to configure it correctly, integrate it with existing tools, and train staff. Getting that wrong at the start creates downstream problems that are expensive to unpick.

OrangeHRM

OrangeHRM is one of the most widely deployed open source HR platforms globally. It covers leave management, time and attendance, recruitment, performance management, and employee self-service. The community edition is free to deploy; the professional and enterprise tiers are paid.

For UK businesses with straightforward requirements and internal IT resource, OrangeHRM is a reasonable choice. The community edition has not always kept pace with the commercial tiers on features, though, which means you may find yourself needing the paid version sooner than expected.

The platform's longevity is a genuine asset. There is a large community, substantial documentation, and a well-understood upgrade path. The UI feels dated compared to newer platforms, which affects adoption rates among staff accustomed to modern SaaS tools.

Odoo HR Module

Odoo is not purely an HR platform. It is a full ERP suite that includes an HR module alongside CRM, finance, inventory, project management, and more. For businesses that need HR as part of a broader operational system rather than a standalone tool, it is worth serious consideration.

The community edition is open source and free. The enterprise edition adds features and official support at a per-user cost. That distinction matters: some of the most useful HR features — including payroll — are only available in the enterprise edition or through third-party modules.

Where Odoo wins is integration. If your business is already running Odoo for finance or operations, adding the HR module avoids the data fragmentation that comes from running separate systems. Employee records, expense claims, project time tracking, and payroll can all live in one place.

The implementation complexity is higher than a standalone HR tool. Odoo deployments benefit significantly from a partner who understands both the platform and the specific configuration requirements for UK businesses. We implement Odoo for UK clients, covering full configuration, data migration, and ongoing support. The Pasalka Enterprises case study is a concrete example — including a 35% reduction in operational costs after eliminating paper-based processes.

Sentrifugo

Sentrifugo is a free, open source HRMS covering employee management, leave tracking, appraisals, and recruitment. It is less widely known than OrangeHRM or Odoo, and its development activity has been inconsistent. For a business evaluating long-term reliability, the maintenance cadence of the underlying project is a legitimate concern.

It is worth including on any shortlist for smaller businesses with simple requirements and strong internal IT capability. It would not be the first recommendation for a growing UK company that needs confidence in the platform's roadmap.

Factorial (Freemium, Not Fully Open Source)

Factorial is sometimes listed alongside open source options because it offers a free tier. It is not open source. It is a SaaS platform with a freemium model. It appears here because UK buyers searching for open source HR software frequently encounter it in comparison lists and assume it belongs in the same category. It does not. The free tier is limited, and the platform scales to paid plans as headcount grows — a different cost model entirely.

Horilla vs OrangeHRM: The Core Comparison

For most UK businesses choosing between open source HR platforms, the decision comes down to Horilla and OrangeHRM. Here is how they compare across the dimensions that matter most.

Feature Completeness

Both platforms cover the core HR functions: employee records, leave management, attendance, recruitment, and performance management. Horilla includes payroll as a module; OrangeHRM's payroll functionality is more limited in the community edition and depends on third-party add-ons or the paid tier for full capability.

Horilla's recruitment module is more developed than OrangeHRM's community edition equivalent — which matters if hiring workflow is a priority. OrangeHRM has a longer feature history in areas like training management.

UK Compliance Readiness

Neither platform ships with UK-specific payroll rules pre-configured. Both require configuration to align with UK statutory leave (28 days including bank holidays for full-time employees), GDPR data handling requirements, and HMRC payroll reporting.

Horilla's modular architecture makes it easier to configure only what is needed without activating complexity you do not require. OrangeHRM's configuration is well-documented but can feel more rigid when handling custom leave types and policies.

Implementation Effort

OrangeHRM has more community documentation, more third-party integrators, and a longer track record. If you are deploying without professional support, the available resources are more extensive.

Horilla is newer and still growing its implementation partner ecosystem. For businesses working with a partner, the implementation path is clear and supported. For self-service deployment, the documentation is adequate but less comprehensive than OrangeHRM's.

UI and Staff Adoption

Horilla's interface is more modern. This is not a trivial point. HR software that staff find confusing or visually dated gets used inconsistently, which defeats the purpose of centralising HR data. OrangeHRM's community edition UI has not changed substantially in several years and shows its age.

Long-Term Maintenance

Both are actively maintained open source projects. OrangeHRM has the longer track record and a larger community. Horilla is growing faster in terms of feature development. For a business committing to a platform for five or more years, the maintenance trajectory matters as much as the current feature set.

What "Open Source" Actually Costs in Practice

The licensing cost is zero. Everything else has a cost.

Hosting. You need a server or cloud environment to run the platform. For a small deployment, this might be a modest monthly cost on AWS, Azure, or a VPS provider. For a larger deployment with high availability requirements, infrastructure costs increase accordingly.

Implementation. Configuring the system correctly, migrating existing employee data, integrating with your payroll provider or accounting software, and training staff all require time. Whether that time comes from internal resource or an external partner, it has a cost.

Ongoing support and upgrades. Open source platforms release updates. Applying those updates without breaking your configuration requires technical oversight. Security patches in particular cannot be ignored.

Customisation. If you need the platform to do something it does not do out of the box, that requires development. The advantage of open source is that customisation is possible. The reality is that it requires developer time.

For a UK business with 20–100 employees, a realistic implementation engagement for Horilla or Odoo HR typically involves initial configuration, data migration, staff training, and a supported go-live period. The total investment is substantially less than a year of SaaS licensing at scale — but it is not zero.

When Horilla Makes Sense for a UK Business

Horilla is a strong fit when:

• You want full control over your HR data and do not want it held on a third-party SaaS platform

• Your headcount is growing and per-seat SaaS costs are becoming a meaningful line item

• You need a modular system covering recruitment, onboarding, leave, attendance, and performance without paying for features you will never use

• You have access to implementation support — either internal technical resource or an external partner

• You want a modern UI that staff will actually use without resistance

It is less suitable when:

• You need payroll processing fully integrated with HMRC submissions out of the box, without any configuration work

• Your IT capability is minimal and you have no budget for implementation support

• You are a very small team (under 10 people) where a lightweight SaaS tool or even a spreadsheet is genuinely sufficient

When Odoo HR Makes More Sense

If HR is one of several operational systems you need to bring under control, Odoo is worth evaluating seriously. The integration between HR, finance, project management, and CRM in a single platform removes the data silos that plague businesses running four or five separate tools.

The implementation is more complex, and the community-to-enterprise edition gap is more pronounced than with Horilla. But for a business also addressing finance, CRM, or inventory in the same programme of work, the combined value of a single platform is significant.

We implement both Odoo and Horilla HRM for UK clients, covering full setup, configuration, and ongoing support. The work we did with Pasalka Enterprises demonstrates what a properly implemented Odoo deployment delivers in operational terms.

The Implementation Question Most Buyers Underestimate

The platform choice matters less than the implementation quality. A well-configured Horilla deployment on modest infrastructure will outperform a poorly configured Odoo deployment on expensive hardware every time.

The businesses that get the most from open source HR software are the ones that invest in getting the configuration right at the start. That means mapping your actual HR processes before touching the system, not after. It means testing leave policies against real scenarios before go-live. It means training HR staff properly — not just giving them a login and hoping for the best.

This is where working with an implementation partner pays for itself. Not because the technical work is beyond a capable internal team, but because the process discipline and the experience of having done this before reduces the time to a working system and the cost of fixing mistakes.

If you are navigating broader technical decisions at the same time — scaling your product team, evaluating your engineering architecture — it is worth understanding how those decisions interact. The fractional CTO guide covers how UK scale-ups are approaching that problem without a full-time hire.

A Note on AI-Assisted HR Workflows

Several HR platforms are beginning to incorporate AI features for recruitment screening, performance review summarisation, and workforce analytics. In the open source space, this is still early. Neither Horilla nor OrangeHRM ships with production-ready AI capabilities that would meaningfully change how HR teams work day to day.

Where AI is making a practical difference is in the systems built around HR data rather than within the HR platform itself. Document analysis, contract review, and onboarding automation are areas where custom AI agents are being deployed by businesses that want to go beyond what any off-the-shelf HR system provides. That is a different conversation from platform selection — but it is worth knowing the boundary exists.

Making the Decision

The right open source HR platform for a UK business depends on three things: the complexity of your HR requirements, your internal technical capability, and whether HR is a standalone need or part of a broader operational overhaul.

For most UK businesses in the 20–200 employee range evaluating open source options in 2026, Horilla is the strongest starting point. It covers the core requirements, has a modern interface, and is actively developed. Odoo is the better choice if you are also addressing finance, CRM, or inventory in the same programme of work.

In both cases, implementation quality determines the outcome more than platform selection. Getting the configuration right, migrating data cleanly, and training staff properly — that is where the investment pays off.

If you are evaluating Horilla or Odoo implementation for your business, we work with UK companies on exactly this. You can learn more at wireapps.co.uk or book a strategy call to discuss your specific requirements.

Frequently Asked Questions

Is Horilla HRM suitable for UK businesses?
Yes. Horilla supports configurable leave policies, attendance tracking, and payroll modules that can be set up to align with UK employment law requirements. It does require configuration during implementation rather than arriving pre-set for UK statutory rules, so working with an implementation partner is advisable for most businesses.

What is the real cost of open source HR software?
The licensing cost is zero, but implementation, hosting, configuration, and ongoing maintenance all carry costs. For a UK business with 20–100 employees, a realistic implementation engagement typically costs significantly less than a year of equivalent SaaS licensing — but it is not a free option in practice.

How does Horilla compare to OrangeHRM?
Horilla has a more modern UI and a more actively developed feature set, particularly in recruitment and payroll modules. OrangeHRM has a longer track record, a larger community, and more extensive documentation for self-service deployment. For businesses working with an implementation partner, Horilla is generally the stronger choice in 2026.

Can Horilla integrate with UK payroll providers?
Horilla's payroll module can be configured for UK payroll requirements, and integration with external payroll providers or accounting software is possible through its API. The specifics depend on which payroll provider you use and what your integration requirements are — this is typically scoped during an implementation engagement.

Should I choose Horilla or Odoo for HR?
If HR is your primary requirement, Horilla is the more focused choice. If you are also evaluating CRM, finance, inventory, or project management and want a single integrated system, Odoo's HR module within the broader ERP suite is worth serious consideration. The implementation complexity is higher with Odoo, but so is the integration value.

What does GDPR compliance look like with open source HR software?
Open source platforms give you full control over where your employee data is stored and how it is processed — which is an advantage from a GDPR standpoint. You are responsible for configuring data retention policies, access controls, and audit logging correctly. A properly implemented Horilla or Odoo deployment can be fully GDPR-compliant; the responsibility sits with the business and its implementation partner rather than a SaaS vendor.

Do I need technical resource to run Horilla long-term?
You need access to technical resource for upgrades, security patches, and configuration changes as your business evolves. This does not have to be a full-time internal hire. Many businesses manage this through an ongoing support arrangement with their implementation partner, covering routine maintenance without the overhead of a dedicated internal role.