ActivityWatch vs Kimai vs Solidtime

These three solve different problems despite sharing the 'time tracking' label. ActivityWatch is a passive, local-first activity logger with no invoicing or…

ActivityWatch

Free (open source) · From Free

Best for: Individuals who want fully automatic background tracking of app, window, and website usage for personal productivity or digital-wellbeing insight, with data that never leaves their own device.

Kimai

Freemium / Open Source · From Free (self-hosted); Kimai Cloud from EUR 2.99/user/month

Best for: Freelancers and agencies that need mature client invoicing, two-factor authentication and SSO, and an extensive plugin ecosystem, whether self-hosted or via low-cost Kimai Cloud.

Solidtime

freemium · From Free

Best for: Freelancers and small agencies who want a modern, simple open-source timesheet and invoicing tool, with a free solo cloud plan and an affordable paid tier once a team is added.

At a Glance

 ActivityWatchKimaiSolidtime
Primary categoryTime TrackingTime TrackingTime Tracking
RatingNot documentedNot documentedNot documented
Pricing modelFree (open source)Freemium / Open Sourcefreemium
Starting priceFreeFree (self-hosted); Kimai Cloud from EUR 2.99/user/monthFree
Free planYesYesYes
Free trialNot documentedYesNot documented
PlatformsWeb, Android, Mac, WindowsWebWeb, Mac, Windows
Team collaborationNot documentedNot documentedNot documented
AI featuresNot documentedNot documentedNot documented
Public APIYesYesNot documented

Standout Differences

Only ActivityWatch tracks automatically without manual time entries

ActivityWatch logs active applications, window titles, and browser activity in the background with no manual timer, while Kimai and Solidtime are both built around users manually logging time against customers, projects, and tasks.

ActivityWatch

Kimai and Solidtime both turn tracked hours into invoices; ActivityWatch does not

Kimai turns logged billable hours straight into client invoices, Solidtime offers that same invoicing capability but only on its Professional plan, and ActivityWatch's documented feature set includes no billing or invoicing capability at all.

Kimai, Solidtime

Kimai is more enterprise-ready with SSO and 2FA

Kimai's documented feature set includes native two-factor authentication (TOTP) plus SSO support for LDAP and SAML, working with identity providers such as Google Workspace and Azure AD, alongside an official plugin ecosystem; Solidtime's provided data doesn't document any comparable authentication or plugin capabilities.

Kimai

Solidtime is the newer, more modern-feeling alternative

Founded around 2024, Solidtime is positioned as a modern alternative to legacy time trackers, but with a smaller feature set and shorter track record than Kimai, which has been in active development since 2006.

Solidtime, Kimai

All three have a genuinely free, self-hostable open-source core

ActivityWatch is entirely free with no premium tiers; Kimai's AGPL-licensed self-hosted core has no user limits or feature paywall; Solidtime's AGPL-3.0 self-hosted core can also be deployed for free indefinitely.

ActivityWatch, Kimai, Solidtime

Feature-by-Feature

Tracking approach

FeatureActivityWatchKimaiSolidtime
Automatic passive tracking of apps, windows, or websitesAvailableUnavailableUnavailable
Manual time entry against clients, projects, and tasksUnavailableAvailableAvailable
Invoicing generated from tracked billable hoursUnavailableAvailableLimited

Data ownership and hosting

FeatureActivityWatchKimaiSolidtime
Free, unlimited self-hosted open-source coreAvailableAvailableAvailable
Data explicitly documented as never leaving the user's own deviceAvailableNot documentedNot documented
Managed paid cloud hosting optionUnavailableAvailableAvailable

Team and enterprise features

FeatureActivityWatchKimaiSolidtime
Multi-user roles and team managementUnavailableAvailableLimited
Two-factor authentication or SSO (LDAP/SAML)Not documentedAvailableNot documented

Pricing Compared

Starting price reflects the lowest paid tier, not the full cost for every team size or usage level.

ActivityWatch

No individual plan breakdown documented yet.

Kimai

Self-Hosted — Free N/A
Kimai Cloud Standard — EUR 2.99/user/month (annual), EUR 3.99 monthly Monthly or annual
Kimai Cloud Professional — EUR 3.99/user/month (annual), EUR 4.99 monthly Monthly or annual

Solidtime

Solo — Free N/A
Professional — 8 euros/user/month (annual) or 9 euros/user/month (monthly) Monthly or annual
Self-Hosted (Open Source) — Free N/A

Pros & Cons

ActivityWatch

Pros

  • Completely free with no premium tiers, usage limits, or ads
  • Strong privacy model — data never leaves the user's device
  • Open source (MPL-2.0) and extensible
  • Cross-platform: Windows, macOS, Linux, and Android

Cons

  • No official iOS app
  • Cross-device data synchronization is still in development
  • As a volunteer-maintained project, support and integrations depend on community contribution rather than a commercial team

Kimai

Pros

  • Free, self-hostable open-source core with no user limits
  • Low per-seat pricing on Kimai Cloud compared to many SaaS competitors
  • Extensive JSON API and plugin ecosystem for customization
  • GDPR-compliant hosting option in Germany
  • Active development with a long project history since 2006

Cons

  • Self-hosting requires server setup and maintenance effort
  • Advanced features like approvals and expense tracking require the Professional plan or plugins
  • Smaller company behind the product compared to large SaaS time-tracking vendors
  • Interface may feel less polished than premium commercial competitors
  • Non-profit discount pricing requires annual billing

Solidtime

Pros

  • Free and open source with the option to self-host indefinitely at no cost
  • Modern, clean interface compared to many legacy time tracking tools
  • Transparent, low-cost paid tier for teams that want a managed cloud version
  • Built-in invoicing and billable rate tracking suited to freelancers and agencies

Cons

  • Newer project, founded around 2024, with a smaller feature set and community than established competitors like Toggl or Harvest
  • Self-hosting requires technical setup and ongoing maintenance
  • Fewer third-party integrations compared to mature commercial time trackers
  • Company size and long-term backing are not well documented, which may concern risk-averse enterprise buyers

Use Cases

Choose ActivityWatch: Individuals who want fully automatic background tracking of app, window, and website usage for personal productivity or digital-wellbeing insight, with data that never leaves their own device.
Choose Kimai: Freelancers and agencies that need mature client invoicing, two-factor authentication and SSO, and an extensive plugin ecosystem, whether self-hosted or via low-cost Kimai Cloud.
Choose Solidtime: Freelancers and small agencies who want a modern, simple open-source timesheet and invoicing tool, with a free solo cloud plan and an affordable paid tier once a team is added.

ActivityWatch

  • Personal productivity tracking — Understand where your time actually goes across apps and websites.
  • Developer time tracking — Track time spent coding directly from your editor via plugins.
  • Digital wellbeing awareness — Build awareness of screen time and app usage habits.
  • Privacy-conscious time tracking — Track time without sending any data to a third-party server.

Kimai

  • Freelance time and invoice tracking — Freelancers track billable hours per client and generate invoices automatically.
  • Agency project time management — Agencies track team hours across multiple clients and projects with approval workflows.
  • Self-hosted internal time tracking — Companies with data-residency requirements self-host Kimai to keep full control of timesheet data.

Solidtime

  • Freelancer Time and Billing — Freelancers track hours per client and project and use billable rates to prepare accurate invoices.
  • Agency Client Time Tracking — Small agencies track time across multiple client projects with role-based access for team members.
  • Self-Hosted Time Tracking — Privacy-conscious teams self-host Solidtime on their own infrastructure to keep time and client data in-house.

Frequently Asked Questions

Which of these tracks time automatically without starting a timer?

ActivityWatch is the only one of the three that tracks automatically in the background, logging active applications, window titles, and (via browser extensions) websites visited, with no manual timer required.

Which tools are suited to billing clients for tracked hours?

Kimai and Solidtime are both built around manual time entry against clients and projects with invoicing generated from recorded hours. ActivityWatch has no billing or invoicing capability in its documented feature set.

Which has the lowest-cost paid cloud plan?

Solidtime's Solo cloud plan is free for individual freelancers, with its paid Professional tier priced at 8 euros per user per month, billed annually. Kimai Cloud's Standard tier begins at EUR 2.99 per user per month billed annually, and drops to EUR 0.99 per user per month for qualifying non-profits and select industries.

Which is the most established, longest-running project?

Kimai has the longest history, tracing back to 2006. Solidtime was founded around 2024. ActivityWatch's founding year is not documented in the provided data, though it is an actively maintained open-source project.

Can all three be self-hosted for free?

Yes. ActivityWatch is a free desktop application with no premium tiers at all. Kimai's AGPL-licensed core can be self-hosted for free with unlimited users. Solidtime's AGPL-3.0 core can also be self-hosted for free indefinitely.

Which one offers enterprise features like SSO and two-factor authentication?

Of the three, only Kimai's provided data documents native two-factor authentication (TOTP) alongside SSO integrations for LDAP and SAML. Neither ActivityWatch nor Solidtime documents comparable authentication features.

Read the full ActivityWatch review · Read the full Kimai review · Read the full Solidtime review