Microsoft Project Gantt Chart: Read It, Edit It, Share It
A Microsoft Project Gantt chart shows tasks as bars, links as lines, critical path in red. Learn to read one and open or edit the file without a licence.
Microsoft retired Project Online on September 30, 2026, per Microsoft's July 2024 announcement, but the desktop Gantt and the .mpp files behind it are everywhere, and most people searching for the "Microsoft Project Gantt chart" were sent a file and do not have the software to open it.
The direct answer: a Microsoft Project Gantt chart draws each task as a bar sized by its duration, joins tasks with link lines, shows the critical path in red, and marks milestones as diamonds. To read a file you were sent, open it in Onplana Schedule, a desktop app for Windows and Mac, which draws the same Gantt from the .mpp.
In short. The Gantt is a picture of schedule data: durations, dependencies, constraints and a baseline. Read the red bars first (the critical path), then the grey baseline bars (the original commitment), then the link lines. To work the plan with other people, import it into Onplana; to audit it once, run the free Schedule Health Check.
How do you read a Microsoft Project Gantt chart?
You read it in a fixed order, because each layer answers a different question. The table lists what each mark means.
| Mark on the chart | What it means | What to ask |
|---|---|---|
| Blue bar | A task, its length is the duration | Is the duration realistic? |
| Red bar | On the critical path (no float) | What else depends on this? |
| Grey bar under a task | Baseline, the committed dates | How far has it drifted? |
| Diamond | A milestone, zero duration | Is it tied to real work? |
| Line with an arrow | A dependency between tasks | Which of the four link types? |
| Dark bar across a group | A summary task | Do its children roll up correctly? |
Start with red. The critical path is the chain where a one-day slip moves the finish date, so it tells you where attention pays. Then compare against grey: a task that sits to the right of its baseline bar has slipped, and a red task that has slipped is a project-level problem. The link types, finish-to-start, start-to-start, finish-to-finish and start-to-finish, each with optional lag, are covered in dependency types explained.
The diagram below shows those layers on one small plan.
Can you open and edit an .mpp Gantt without Microsoft Project?
Yes. Onplana Schedule opens .mpp, .mpx and Microsoft Project XML from the desktop, and also Primavera P6 .xer, ProjectLibre .pod and GanttProject .gan files. It shows the Gantt and a grid with name, duration, start, finish, predecessors, resources and percent complete, plus outline, critical path, float, milestones and baseline bars when the file carries them. Downloads for Windows and Mac are at /schedule; the open an MPP file post walks the steps, and what an MPP file is explains the format.
Editing works the way you would expect: undo, insert, delete, indent, outdent, links drawn by drag with type and lag, and all eight constraint types with deadline warnings. Every change reschedules the plan. It saves Microsoft Project XML as a new file beside the original, which Microsoft Project opens; it does not write the .mpp format and never overwrites your source.
What happens to the file when you open it?
The file's contents decide, not its extension. Both halves:
- Microsoft Project XML: read on your machine. Nothing is uploaded.
- Everything else: a binary .mpp, or a Primavera P6 or Planner XML export, is converted on Onplana's servers, and the uploaded copy is deleted within 24 hours.
A ProjectLibre .pod is checked on open: if its contents turn out to be Project XML, it is read locally and nothing is uploaded. If nothing may leave your machine, ask the sender for a Project XML export.
How do you share a Gantt chart with people who have no Project?
Pick by what the others need to do. For a one-way view, export a PDF from Onplana Schedule. For a team that needs to work the same plan together, import it: the importer takes .mpp, MSPDI .xml, .xer and Excel or CSV, and keeps tasks, hierarchy, four dependency types with lag, all eight constraint types, custom fields, milestones and costs. The Gantt, critical path and baselines are on every Onplana plan including Free, so nobody needs a paid seat to see the schedule; see the Gantt chart with critical path page for what it shows, and what a Gantt chart is for the basics.
Is a clean-looking Gantt a healthy schedule?
No. A tidy Gantt can hide missing links, hard constraints and negative float. Before you trust or share a plan, run the free Schedule Health Check on the file; it reads up to 20 MB and 20,000 tasks and lists the findings. The seven most common are in schedule health check: seven things.
Run the free Schedule Health Check Upload the .mpp you were sent and get a list of what is wrong with the schedule behind the Gantt, in under a minute. No signup required. → Open the Schedule Health Check
Microsoft Project™ is a trademark of Microsoft Corporation. Onplana is not affiliated with Microsoft.
Frequently asked questions
What is a Microsoft Project Gantt chart?
It is the timeline view of a Microsoft Project plan: each task is a horizontal bar sized by its duration, link lines show which task waits for which, the critical path is drawn in red, and milestones appear as diamonds. The bars are a picture of the schedule data behind them, not a separate drawing.
How do I read the red bars on an MS Project Gantt chart?
Red bars are the critical path, the chain of linked tasks with no float, so a slip on any one of them moves the project finish date. Grey bars underneath the task bars are the baseline, the dates the plan was committed at.
Can I open a Microsoft Project Gantt chart without Microsoft Project?
Yes. Onplana Schedule, a desktop app for Windows and Mac, opens the .mpp file and draws the same Gantt with critical path, float and baseline bars when the file carries them. The free Schedule Health Check reads a file in the browser if you only need an audit.
Is my file uploaded when I open it?
It depends on what is inside the file, not its extension. If the contents are Microsoft Project XML, the file is read on your machine and nothing is uploaded. Anything else, including a binary .mpp, is converted on Onplana's servers and the uploaded copy is deleted within 24 hours.
Can I edit the Gantt and save it back to .mpp?
You can edit it, but not save to .mpp. Onplana Schedule saves Microsoft Project XML as a new file beside the original, which Microsoft Project opens, and it never overwrites your source file.
How do I share a Microsoft Project Gantt chart with people who do not have Project?
Export a PDF from Onplana Schedule for a one-way view, or import the plan into Onplana so the team works the same schedule together. Sending the .mpp itself only helps people who already have software that opens it.
Does a Gantt chart replace a schedule health check?
No. A Gantt makes problems visible only if you know where to look; missing links, hard constraints and negative float can all sit behind a plan that looks tidy. A health check reads the same data and lists them.
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