Free XER viewer
Yes, a Primavera P6 .xer schedule opens without Primavera: in Onplana Schedule, the free Windows and Mac app that shows the Gantt chart and critical path and edits the plan, or right here in your browser.
An .xer file is converted on Onplana's servers to open it. The viewer asks before it uploads a copy, and the uploaded copy is deleted within 24 hours. Updated .
Want to edit the plan, level it, compare two versions or save it? Get Onplana Schedule, free for Windows and Mac
How do I open an XER file without Primavera P6?
- Choose Open a file above, or drop the .xer onto the viewer.
- The viewer asks before it sends a copy to be converted. An .xer is Primavera's own text format, so the conversion is the step that reads it; the copy is deleted within 24 hours.
- Read the plan: switch between the Gantt chart and the task table, show the critical path, open an activity for its details, and run the free health check.
- To edit, level resources, compare two versions or save, open the same file in Onplana Schedule on Windows or Mac.
Holding a Microsoft Project file instead? The online MPP viewer is the same screen for .mpp and Project XML. Weighing the two schedulers against each other is the blog's Project Online vs Primavera P6 comparison.
What is an XER file?
An XER file is Primavera P6's own export: a tab-delimited text file holding a project's activities and WBS, their relationships, calendars, resources and assignments, written by P6 through File > Export and read back through File > Import. Because it is text rather than a sealed binary, other schedulers can read it. The converter behind this viewer and behind Onplana Schedule is MPXJ, the open-source library whose documentation lists Primavera P6 XER and PMXML among the formats it reads and writes (mpxj.org, read October 6, 2026). Onplana Schedule opens .xer files through that same converter, and when two P6 versions of one schedule are compared it matches them by Activity ID, the identifier P6 keeps when a project is copied.
What does a P6 viewer show from the file, and what does it not?
Shows
- Activities in their WBS outline, as a Gantt chart and a task table
- Durations, start and finish dates and percent complete
- Relationships of all four types, with their lag
- Constraints, as a column in the table
- The critical path and float, computed from the links in the file
- The details of any activity
Does not, and what happens instead
- A baseline. P6 keeps a baseline as a separate baseline project, so the schedule file carries none and the Baseline toggle has nothing to show.
- Editing in the browser. This viewer is read-only; the desktop app edits.
- Saving back as .xer. Onplana Schedule saves Project XML, which P6 Professional imports.
- Files over 20 MB here, or over 50 MB in the desktop app and the workspace import.
Bringing the plan into a shared workspace rather than a viewer? The import and export page lists what comes across from a P6 file, and the construction scheduling software page says where the field-operations line is.
Which XER viewer should you use?
This page for a look, Onplana Schedule for the work, and Onplana project management when the whole team needs the plan. All three read the same converted file.
| Decision | The online viewer above | Onplana Schedule, the desktop app | Onplana project management, imported |
|---|---|---|---|
| Best for | A one-off look at a file you were sent, with nothing installed. | A planner who opens P6 files regularly and wants to edit, level, compare versions and save. | A team that will work the P6 plan together in a browser and track it against a baseline. |
| Price | Free, no account. | Free, no account until you publish a copy. | Free for up to 5 members and 2 projects, then from $7 per seat per month. |
| Edits the plan | No. Read-only. | Yes: names, durations, dates, predecessors, constraints and percent complete; insert, delete, indent and outdent; undo. | Yes, by everyone with access, on the Gantt and in the task list. |
| Saves as | Exports the chart as a PDF or picture and the table as a CSV. | Project XML, never .xer. P6 Professional imports Project XML. | Project XML, Excel and a Gantt PDF; the plan itself lives in the workspace. |
| File size | Up to 20 MB. | Up to 50 MB. | Up to 50 MB. |
| Where the file is read | Converted on Onplana's servers after you say so; the uploaded copy is deleted within 24 hours. | The same conversion, after the app asks; the converted schedule then stays on your machine. | Uploaded into your own workspace, where the plan stays. |
| When NOT to choose it | When you need to change anything, or to keep working with no connection. | When the file has to go back to P6 as an .xer, or when a baseline must come from the file. | When you only want to look once, or your schedule depends on sub-day lag (the web app moves in whole working days). |
Is there a Primavera P6 viewer that is free and edits too?
Onplana Schedule is a free app for Windows and Mac that opens a P6 .xer as a Gantt chart with the critical path and float, edits it (names, durations, dates, predecessors in Project's own notation, constraints, percent complete), levels resources, compares two versions by Activity ID, scores the schedule against the DCMA 14-point checks, and saves the result as Project XML. No account until you publish a copy to share.
Everything the app does, and the exact privacy sentence it shows before a conversion, is on the Onplana Schedule page.
Frequently asked questions
Do I need Primavera P6 installed to open an .xer file?
No. The viewer above converts the file and draws the Gantt chart and the task table in your browser, and Onplana Schedule does the same on Windows and Mac, with editing. Neither needs a Primavera licence or an account.
Is my XER file uploaded?
Yes, to be converted: an .xer is Primavera's own format, and the converter runs on Onplana's servers. The viewer asks before it sends a copy, until you tick Don't show this again, and the uploaded copy is deleted within 24 hours. Nothing else is uploaded unless you run a health check or publish a copy.
Can I edit the schedule and send it back to Primavera P6?
You can edit it in Onplana Schedule, the free desktop app, which saves as Project XML rather than .xer. Primavera P6 Professional can import that file through File > Import > Microsoft Project, for an admin superuser, with custom fields mapped to P6 user-defined fields during the import. The .xer you opened is never changed.
Why does the Baseline toggle show nothing?
Because a P6 .xer carries no baseline: P6 keeps a baseline as a separate baseline project rather than inside the schedule, so there is nothing in the file to draw. In Onplana Schedule, open the baseline project with Compare with another version to see the two side by side; in Onplana project management, capture a baseline right after the import.
How large a file can it open?
Up to 20 MB in the browser. Onplana Schedule and the workspace import take files up to 50 MB.
Can I compare two versions of a P6 schedule?
Yes, in Onplana Schedule. Open one version, choose Compare with another version and pick the other file: two P6 versions are matched by Activity ID, the identifier P6 keeps when a project is copied, and you get the finish that moved, the changed activities on the path to it, what was added or removed, and a CSV of every change.
Can my team work the P6 plan together?
Yes. Import the .xer into Onplana project management, on every plan, including Free, and everyone opens it in a browser with the critical path, dependencies and milestones intact. Capacity across projects is on the Professional plan and up. The import page lists exactly what comes across.
Does the XER viewer work on a Mac?
Yes. This viewer runs in any current browser, and Onplana Schedule runs on macOS 13 or later as well as Windows 10 (version 1809) or later.