A backlog is an ordered list of work still to be done, usually written as user stories and prioritized by the business, used to manage and organize the work of an adaptive or agile project. It reflects the current needs of the project, including product requirements and user stories, and it holds a continuously reprioritized plan for the remaining work.
The word doing the heavy lifting there is ordered. A backlog is not a list of everything anyone has ever asked for. It is that list sorted, so that the question “what next?” has exactly one answer at any moment.
The three backlogs
PMBOK 8 names three types that adaptive and agile projects commonly use. They are nested, not alternatives.
| Backlog | Contains | Usually owned by |
|---|---|---|
| Product backlog | Requirements, features, epic user stories and user stories — the overall scope and vision of the product | The product owner |
| Release backlog | The subset planned for one specific release, which may span several sprints or iterations | Product owner with the team |
| Iteration backlog | The selected user stories plus the tasks needed to finish the work committed for the current iteration | The development team |
The distinction between the product backlog and the sprint or iteration backlog is the one PMBOK 8 flags as most worth keeping straight: the first holds the complete list of desired features and changes, the second only the subset selected for delivery in a specific iteration.
How the backlog replaces change control
This is the part that surprises people coming from predictive projects. In adaptive approaches, PMBOK 8 says change is managed through backlog management rather than a formal change request process. When a stakeholder proposes something:
- It is recorded as a product backlog item and added to the backlog.
- An impact analysis is still performed, to evaluate the effect and set the priority. The analysis does not disappear, only the paperwork around it.
- There is typically no formal approval step. Assigning the item a low priority is the deferral. Choosing not to add it, or removing it, is the rejection.
Items are ranked by business value or importance to the customer and sized by the development team, so the highest-value items are selected for the next development cycle. Dependencies and constraints are taken into account, which can change where a new item lands in the order.
Backlog refinement
Refinement is the progressive elaboration of what is in the backlog, together with its reprioritization, to identify the work that can be accomplished in an upcoming iteration. In practice it means constantly reviewing, revising, ranking and editing the product backlog so the team builds what the business and the customer actually need.
Two things make refinement work. Items near the top are small and clear enough to start; items further down can stay coarse. And the session ends with an order, not a discussion. A refinement meeting that produces no reprioritization has not refined anything.
Backlog in PMBOK 8
- Own entry in Section 4, Inputs and Outputs (p. 114). Backlog is defined there in full, with the three types listed underneath.
- Output of Develop Scope Structure (Figure 2-17). The product backlog appears as an output alongside the scope baseline, the work breakdown structure, the WBS dictionary and user stories. In agile projects, the guide states, the WBS corresponds to the product backlog, where work items can be broken down into epics and user stories.
- Input to Monitor and Control Schedule (Figure 2-24). The product backlog sits next to the project management plan as an input, and backlog refinement is listed there as a tool and technique.
- Tool and technique of Assess and Implement Changes (Figure 2-10). Backlog management appears in the same list as integrated change control, which is the clearest statement of the two parallel routes for handling change.
- Backlog management and backlog refinement each have their own entry in the tools and techniques section (p. 148).
- Scope baseline equivalence. For adaptive approaches, the guide notes the scope baseline may be called prioritized requirements or the sprint backlog.
In practice
- One order, no ties. If two items are both “high priority”, the backlog has failed at its only job. Force the ranking.
- A backlog is not a parking lot. Items that have sat below the line for a year are noise. Deleting them is a legitimate decision, and PMBOK 8 treats removal as the equivalent of rejecting a change.
- Size before you commit, not before you rank. The business ranks by value; the team sizes what is near the top. Estimating the whole backlog is wasted effort.
- Watch the growth rate, not just the count. A backlog that grows faster than velocity is telling you something about scope discipline that no status report will.
- Keep acceptance criteria on the item. PMBOK 8 ties iteration closure to confirming that prioritized backlog items are finished and all acceptance criteria are met.
FAQ
Is a backlog the same as a to-do list?
No. A to-do list is a set of tasks; a backlog is a ranked set of value propositions, written from the user’s point of view and reordered as the project learns. The ordering and the ownership are what make it a backlog.
Who owns the backlog?
The product backlog is normally prepared and kept current by the product owner, who represents the business. The iteration backlog belongs to the team, because that is where the commitment lives. Mixing the two is how teams end up being told both what to build and how much to commit to.
Does a predictive project have a backlog?
Not in this sense. Its counterpart is the scope baseline: scope statement, WBS and WBS dictionary, changed only through formal change control. Some hybrid projects keep a baseline for contracted scope and a backlog for the discretionary part.
Does a backlog mean there is no scope creep?
It means uncontrolled growth shows up differently. Nothing stops a backlog from expanding indefinitely; the discipline is in the ranking and in the willingness to remove items, not in the container.
How big should a backlog be?
Big enough to cover the next few iterations in detail and the foreseeable release in outline. Beyond that, detail decays faster than it is used. That is the point of refining continuously rather than specifying up front.
Is a backlog an artifact or a technique?
Both, in PMBOK 8 terms. The backlog itself is an input and output described in Section 4; backlog management and backlog refinement are tools and techniques described in Section 5.
By Tom, PMP-certified since 2004. Last updated: August 2026.