Open Source Gantt Chart
The bars in a Gantt chart are the easy part. The hard part is the engine underneath them: real task dependencies, calendars, and resource limits that recompute the whole timeline the moment one task slips a week. A tool that only draws bars leaves you re-entering dates by hand and hides schedule risk in the process. Open source options matter here because the plan you build is a dense graph of tasks, durations, and links you may need to reopen, reschedule, or hand off years later, and keeping that graph in files or a database you control means the schedule you spent days constructing stays yours to recalculate rather than rebuild.
OpenProject
Web-based project management software for planning, agile work, and time and cost reporting
Leantime
Open source project management for non-project managers, built with ADHD, dyslexia, and autism in mind
GanttProject
Free desktop project management app with Gantt charts, dependencies, and export to PDF, HTML, and PNG
TaskJuggler
Free and open source project management software with optimizing scheduling and reporting
LibrePlan
Open source web-based project management for planning, monitoring, and control
Our picks
Best for scripted, optimizing schedules: TaskJuggler TaskJuggler is for planners who want the schedule computed, not drawn. You describe the project in a plain text file, and its optimizing scheduler assigns resources, levels load, and resolves conflicts, with unlimited scenarios for what-if analysis and HTML, CSV, and iCalendar reports. There is no graphical editor, so it suits text-editor users.
Best for resource-heavy planning: LibrePlan LibrePlan is the pick when shared people and machines drive the plan as much as task order. It models resources with reusable calendars, plans against a multi-level work breakdown structure, and reallocates automatically to reduce overload, with Monte Carlo completion dates and earned value tracking. It runs on Java with PostgreSQL or MySQL, so a whole team keeps the schedule current.
Best for team project management: OpenProject OpenProject fits teams that want scheduling inside a broader project system rather than a standalone chart. It combines classic, agile, and hybrid planning with work packages, roadmaps, time tracking, cost reporting, and budgeting, and links work packages to GitHub pull requests. The free self-hosted Community Edition suits a Gantt view that also needs comments and permissions.
Best for a single desktop planner: GanttProject GanttProject is the straightforward desktop choice for one planner who wants a chart without a server. It handles task hierarchy, dependencies, milestones, and baselines, generates an optional PERT chart, and exchanges files with MS Project and Excel while exporting to PDF, HTML, and PNG. Collaboration is file-based over WebDAV, awkward once several people edit one plan.
Matching the scheduling engine to your project
The first thing to test is whether a tool actually schedules or merely charts. A real scheduler takes your task hierarchy, dependencies, durations, and calendars and computes the timeline, moving downstream dates when an upstream task slips and flagging the critical path. TaskJuggler and LibrePlan sit at this end, with optimizing schedulers and resource leveling that resolve conflicts for you; GanttProject draws dependencies and baselines but leans on you to keep dates coherent. Change one upstream task in a trial project and confirm the downstream dates actually move before you trust the chart.
Next, decide whether the schedule is a personal planning file or a shared system of record. GanttProject is a desktop app one planner can own and keep offline, which is simple until several people need to edit the same plan. OpenProject and Leantime are web applications that add accounts, permissions, comments, and progress updates across a team, at the cost of hosting, upgrades, and authentication. TaskJuggler is different again: you write the plan as a text file and it generates reports, which suits planners comfortable in a text editor and version control.
Finally, weigh resource planning against pure sequencing. If your work depends on shared people or equipment, overbooking is as dangerous as a missed dependency. LibrePlan models workers and machines with reusable calendars and automatic reallocation, and TaskJuggler handles leave, shift work, and multiple time zones; a bar chart with named assignees will not warn you when the same crew is booked twice. Test the tool with real resource conflicts across overlapping tasks, not just a clean single-planner example.
Related categories
Frequently asked questions
What separates a real scheduler from a tool that just draws bars?+
A scheduler computes the timeline from your inputs: it reads dependencies, durations, and calendars, then moves dates automatically when something changes and derives the critical path. A bar drawer stores dates you type in and leaves the logic to you. TaskJuggler and LibrePlan compute schedules and level resources; simpler tools mostly render bars. The quick test is to shift one upstream task and see whether downstream dates follow.
Do these tools calculate a critical path I can trust?+
Some compute it properly and some only approximate scheduling. Critical path is only meaningful when calendars, durations, and dependency types (finish-to-start, start-to-start, lag, and lead) are all consistent. TaskJuggler's optimizing scheduler and LibrePlan's planning engine are built for this. Before relying on it, change a single task and confirm the calculated path and downstream dates update, because a pretty chart with manual dates can hide real slippage.
Which of these fits a solo planner versus a whole team?+
For one planner who wants offline control, GanttProject is a self-contained desktop app, and TaskJuggler suits a planner who prefers writing the schedule as a text file. For teams that update progress, comment, and need permissions, OpenProject and Leantime are web applications built for shared use. The trade is that the web tools add hosting, authentication, and upgrade work that a desktop file does not.
How well do these import Microsoft Project files?+
Import is usually partial. Commercial project files carry scheduling rules, calendars, custom fields, and resource settings that may not map cleanly. GanttProject exchanges data with MS Project and Excel, so task names and dates tend to survive, while baselines, resource assignments, and constraints are less reliable. Always test with a real file and compare dependencies, durations, milestone dates, and calendar exceptions before trusting the migrated plan.
Which tools handle resource leveling and overbooking?+
If shared people or equipment drive your plan, look for real leveling rather than plain assignees. LibrePlan models workers and machines with reusable calendars and reallocates automatically to reduce overload, and TaskJuggler levels resources while handling leave, shift work, and time zones. Test the tool by assigning the same person or machine across overlapping tasks and checking whether it warns you about the conflict.
Do I need baselines, and which tools keep them?+
Baselines matter when you must measure variance against an approved plan instead of overwriting history each week. Without them, every update erases the evidence of slippage or recovery. GanttProject supports baselines directly, and TaskJuggler's unlimited scenarios let you compare what-if plans against a reference. For contract work, steering meetings, or postmortems, that comparison is often more valuable than extra chart styling.
Can I run a Gantt chart without a graphical editor?+
Yes. TaskJuggler has no graphical interface at all: you describe the project in a plain text file, run the scheduler, and read HTML, CSV, or iCalendar reports served by its built-in web server. That suits planners who want the schedule under version control and scriptable, and it removes the drag-and-drop layer entirely. If you prefer a visual editor, GanttProject or a web tool like OpenProject will fit better.