1,919 tools
Free planSoftware & utilities
OpenSign is an open source PDF e-signature platform positioned as an alternative to commercial signing tools. It offers unlimited free signatures, multi-party signing, completion certificates with access logs, secure document storage in OpenSign Drive, self-hosting, and developer API documentation from OpenSign Labs.
Free to startSoftware & utilities
OpenSIPS is a mature open source SIP server and application platform for voice, video, IM, and presence services. It provides a modular, scriptable routing engine aimed at carrier-grade performance, with documentation, benchmarks, monitoring interfaces, and a web configuration UI for VoIP architects and operators.
Free planSoftware & utilities
OpenSky Network is a nonprofit research platform that collects and publishes open air-traffic sensor data including ADS-B, Mode-S, ADS-C, FLARM, and VHF feeds for aviation research. The site offers live maps, historical databases, scientific datasets, and API access so universities and analysts can study global flight patterns.
Free planSoftware & utilities
OpenStreetMap is a collaborative project that builds a free, editable map of the world from community contributions. Mappers add and maintain roads, trails, stations, and points of interest using open data licensing, powering thousands of apps, devices, and humanitarian mapping efforts worldwide.
Free to startSoftware & utilities
OpenTripPlanner is an open source family of projects for multimodal passenger information and transportation network analysis. Its Java server builds itineraries combining transit, walking, bicycling, and driving using OpenStreetMap and GTFS data, exposed through web APIs and client libraries used by regional journey planners worldwide.
Free planSoftware & utilities
OpenTTD is an open source simulation game based on Transport Tycoon Deluxe that recreates and extends the classic transport-building gameplay. It adds larger maps, stable multiplayer for many players, dedicated servers, IPv6 support, NewGRF customization, and numerous quality-of-life tools under the GPL v2 license.
Free tier unknownSoftware & utilities
OpenVAS is the Open Vulnerability Assessment Scanner maintained in the Greenbone ecosystem for finding security issues in networks and hosts. The openvas.org site introduces OPENVAS by Greenbone as a vulnerability scanner project with links to Greenbone community and commercial offerings.
Free planSoftware & utilities
OpenVDB is an open-source C++ library and file format for efficiently storing and manipulating sparse volumetric data such as smoke, fire, and other FX volumes. The project site welcomes visitors to documentation, downloads, and community resources for integrating OpenVDB into DCC tools and renderers.
Free planSoftware & utilities
OpenWA is a free, open source, self-hosted WhatsApp HTTP API gateway for developers who want full control of messaging infrastructure. It provides REST endpoints, multi-session support, webhooks, a web dashboard, pluggable databases and storage, optional Redis queues, and swappable WhatsApp engines without vendor lock-in.
Free planSoftware & utilities
Apache OpenWhisk is an open-source serverless platform that runs functions in response to triggers from HTTP requests, feeds, or scheduled rules. The project packages actions in containers, exposes a REST API and wsk CLI, and supports multiple language runtimes so teams can self-host event-driven workloads at scale.
Free to startSoftware & utilities
Operational is an open source event tracker built for tech products and SaaS operators who need a live feed of signups, payments, webhooks, cron jobs, and errors.
Free tier unknownSoftware & utilities
Orderli provides QR ordering for hospitality venues, letting guests order from mobile menus that integrate with existing POS systems. It advertises fixed monthly fees without setup charges, optional annual billing discounts, and transparent payment processing fees per method.
Free trialSoftware & utilities
Phase Two Organizations is a Keycloak extension for multi-tenant B2B identity, adding organization-aware invitations, authorization, and self-management on top of managed Keycloak hosting. The product page targets SaaS vendors that need per-customer orgs, SSO, and customizable auth flows without rebuilding IAM primitives.
Free planSoftware & utilities
Ory provides identity, authentication, authorization, and OAuth2/OIDC services through Ory Network and related open-source projects such as Kratos, Hydra, and Keto. The commercial site targets CIAM, B2B IAM, fine-grained permissions, passkeys, and enterprise SSO for applications that need scalable, API-first identity infrastructure.
Free tier unknownSoftware & utilities
OS3 designs and builds HALE 1.0, a US-made bimanual mobile robot trained with video demonstrations. It deploys the platform in hospitality laundry today while selling developer units and partner programs for other semi-humanoid applications.
Free tier unknownSoftware & utilities
Oscr replaces long email chains with a client portal where customers answer transaction questions in minutes so bookkeepers can close books faster. The marketing site focuses on waitlist signup for firms tired of chasing client responses.
Free planSoftware & utilities
Open Source Social Network (OSSN) is a free PHP social network script for building self-hosted community sites with profiles, timelines, groups, messaging, notifications, and media sharing. The project emphasizes data sovereignty, REST APIs, themes and components, and optional commercial hosting or marketplace add-ons.
Free planSoftware & utilities
osTicket is a widely used open-source customer support ticketing system for help desks and shared inboxes. The official site promotes the downloadable open-source edition plus optional cloud trials while linking setup guides, downloads, and community resources for teams handling email, web, and API-created tickets.
Free tier unknownSoftware & utilities
OtherYou.io hosts a minimal React single-page application shell with little public marketing copy in static HTML.
Free planSoftware & utilities
Otixo.com now redirects to We.Team, a German collaboration suite that combines realtime chat, file sharing, cloud drive aggregation, and We.Team Meet video conferencing. Teams work in TeamSpaces and Channels with desktop, browser, and mobile clients plus optional TeamSpace Business upgrades.
Free planSoftware & utilities
Otterwatch monitors SSL certificate expiry and site reachability with daily checks on the free tier and deeper TLS analysis on Pro. The service emails subscribers when certificates approach expiry or when sites go down, emphasizing plain-text alerts and a calm, no-tracker experience.
Free planSoftware & utilities
An Otter Wiki is a minimalistic, self-hosted wiki powered by Python, Markdown, and Git. It offers markdown editing with attachments, extended syntax including tables and Mermaid diagrams, git-backed history, user authentication, and dark mode in a lightweight interface documented on the official project site.
Free to startSoftware & utilities
Outline helps people run their own VPN to access the open internet more safely. It combines the Outline Manager desktop app to deploy servers on chosen cloud providers and the Outline Client apps to connect with access keys, using open source, audited technology designed to resist common blocking techniques.
Free tier unknownSoftware & utilities
Outschool is a marketplace for live online classes for learners ages 3–18 across more than 140,000 listed subjects. Families browse educator-led sessions, enroll per class, and access interactive learning outside traditional school schedules.
Showing 1,368 of 1,919 tools
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