If you’ve worked on a backend system, you know that, while products do change through big launches, they also experience a quieter and more constant evolution: small updates. For example:
- A flag flips.
- A column gets added.
- A permission rule tightens.
- A response shape changes by one field.
In backend terms, these changes usually show up as PUT and PATCH requests.
PUT and PATCH requests definitely don’t get a big product launch—actually, they may not even make it into release notes—but that doesn’t mean they’re not important. In fact, they can be one of the determining factors of whether a system scales cleanly or slowly collapses.
The incomplete mental model
When learning the basics of backend engineering, developers are usually taught something like this:
- POST creates
- GET reads
- PUT updates
- DELETE removes
PUT makes it into this list, and is thus framed as the “real” update verb—the serious, canonical way to change a resource. PATCH, on the other hand, is usually just taught as a brief addendum—usually described as a “partial update.” In other words, optional and easy to ignore.
That framing misses what really matters, though. PUT and PATCH don’t just “update” data in different ways; they encode fundamentally different assumptions about ownership, authority, and evolution of state. Understanding that difference is key to designing APIs that stand the test of time.
PUT: Declaring the full state
A PUT request is declarative by nature. When a client sends a PUT, it is effectively saying: “This resource should now look exactly like this—no more, no less.”
There is no notion of “merge this” or “change just one thing.” The payload represents the full, authoritative state of the resource. Anything omitted is intentionally omitted. Anything included replaces what was there before. PUT is about state replacement.
That makes it powerful, and risky.
PATCH: Expressing intent
PATCH takes a very different stance from PUT. Instead of replacing state, it expresses intent: “Given whatever this resource looks like right now, apply only these specific changes.”
Everything else remains untouched, which makes PATCH far more forgiving in real-world systems where clients are frequently out of date, payloads should be small, and multiple actors may be interacting with the same resource. PATCH is about state mutation, not state replacement.
It’s forgiving, practical, and optimized for real usage patterns where:
- Clients may be out of date
- Payloads should be small
- Multiple actors update the same resource
Nobody updates their entire profile just to change their bio. PATCH matches how people actually use software.
Why the difference matters
At a small scale, PUT and PATCH feel interchangeable. But in a real production system, they diverge fast. That’s because using PUT where PATCH is appropriate causes accidental erasure. For example:
- Old clients drop new fields
- Partial payloads overwrite data
- Integrations unknowingly remove state
Nothing crashes. The system just does exactly what it was told to do—which may have consequences you didn’t intend (like all of the above).
On the flip side, using PATCH where PUT is appropriate causes state drift. For example:
- Old fields linger
- Invariants weaken
- Data becomes harder to reason about
PUT isn’t inherently better than PATCH, and PATCH isn’t inherently better than PUT—but one of those choices can be very wrong when misapplied.
How to choose between PUT vs. Patch
So you understand what they are and you understand why it matters. Now the hard part: How do you know when to choose?
Here’s a quick cheatsheet.
PUT works best when:
- The client owns the full schema
- Consistency matters more than flexibility
- You’re syncing a canonical source of truth
Think admin panels, configuration editors, or tightly controlled internal tools. PUT forces clarity about who controls the resource, and it leaves little room for ambiguity.
PATCH, on the other hand, works best when:
- The client does not own the full schema
- Flexibility matters more than strict consistency
- Multiple actors may update the same resource
- You expect clients to be out of date or partially informed
Think user profiles, collaborative records, or public-facing APIs where change is frequent and unpredictable. PATCH allows the system—not the client—to remain the ultimate source of truth about the full resource. It reduces friction, limits risk, and aligns with how real users (and real integrations) actually behave in production.
How this shows up in Xano
In Xano, choosing PUT vs. PATCH isn’t cosmetic. It defines:
- How much authority a client has
- How resilient your API is to change
- How safe future schema updates will be
PATCH endpoints are intentionally tolerant. PUT endpoints are intentionally strict.
Early-stage products often lean heavily on PATCH because it’s flexible and forgiving. As systems mature, teams tend to introduce more PUT endpoints in places where state needs to be tightly controlled. Both have a place; the key is knowing when to use each.
Security implications
There is also a subtle but important security dimension to this choice.
PUT tends to expand the blast radius of mistakes, since replacing full state means any error can have widespread impact. PATCH, by contrast, naturally limits damage to only the fields being changed.
This is why PATCH pairs well with user-driven updates and field-level permissions, while PUT is often more appropriate for admin-only or internal actions. In practice, your choice of HTTP method becomes part of your security model, not just your API design.
Designing with intent
Most inconsistent APIs don’t start that way—they grow that way. Endpoints get copied. Logic gets reused. Shipping wins over perfection. Eventually, it’s worth stepping back and asking a few foundational questions:
- Is this endpoint replacing state or mutating it?
- Should missing fields be destructive or ignored?
- Who defines the “full truth” of this resource?
Once you’re clear on those answers, the choice between PUT and PATCH usually becomes obvious.
Final thought
Most production systems live or die on the boring stuff. Not major launches, but the thousand small changes made safely over time.
PUT and PATCH exist to manage that reality. Used deliberately, they let your backend evolve without fear. Used casually, they quietly undermine everything built on top.
Your system’s future isn’t shaped by what you add. It’s shaped by how you change what already exists.
For more on designing reliable APIs, check out a few other blogs by the Xano team below. Ready to start building? Get Xano for free.
