I needed up-to-date .NET mapper benchmarks. They didn't exist.

Jagoba Inda Arizaleta — Wed, 24 Jun 2026 01:28:39 +0000

The day AutoMapper stopped being a no-brainer

For years, AutoMapper was the default. You added the NuGet package, wrote a profile, and never thought about it again. That changed for me in 2025.

Two things happened almost back to back:

AutoMapper went commercial. On July 2, 2025, Jimmy Bogard announced commercial editions of AutoMapper (and MediatR) under a new company, Lucky Penny Software. It's still free for individuals and companies under $5M USD in annual revenue, but above that you now need a paid license. (announcement)
The last freely-patchable version got a high-severity CVE. CVE-2026-32933 (CVSS 7.5, High) is a Denial-of-Service via uncontrolled recursion: map a deeply nested object graph and you get a StackOverflowException that takes the whole process down, and in modern .NET you can't even catch it. The catch? The fix landed in the paid versions (15.1.1 / 16.1.1).

So if you're on the free track, you're sitting on a known DoS with no free upgrade path. At work, that meant one thing: we had to migrate AutoMapper out of every project.

The problem: nobody had fresh numbers

There's no shortage of candidates: Mapperly, Mapster, TinyMapper, AgileMapper, or just writing the mapping by hand. The hard part wasn't finding options, it was figuring out which one to actually trust in production, and that's a call you want to make with data, not vibes.

I went looking for benchmarks and hit a wall:

Most comparisons were years old.
None were run against .NET 10.
Library versions were stale, so the conclusions no longer applied.
Everyone benchmarked slightly different scenarios, so you couldn't compare apples to apples.

Performance characteristics change with every runtime and every library release. A benchmark from 2021 tells you almost nothing about Mapperly 4 on .NET 10. I didn't want a snapshot. I wanted something that stays true over time.

So I built it.

The solution: benchmarks that never go stale

I built a BenchmarkDotNet runner that measures the major .NET mappers across consistent scenarios, plus a small landing page to read the results.

What makes it different from the "I benchmarked these one afternoon in 2022" posts:

It runs every hour on a dedicated VPS, automatically.
Library versions auto-update to the latest release, so the numbers always reflect what you'd actually install today.
Results are averaged over the last 3 months to smooth out noise and show long-term trends, not a single lucky run.
No raw JSON, no markdown walls, just clean, interactive charts.

What I measure

Four scenarios that cover the cases you hit in real code:

Scenario	What it stresses
`SimpleFlat`	Flat POCO to POCO, identical names
`NestedObject`	Object graphs with nested types
`Collection`	Mapping lists/arrays of objects
`NameDifference`	Source/target with mismatched property names

For each one: mean execution time (μs) and memory allocated per operation (bytes).

Why I'm not posting the numbers here

This is the part where a normal post drops a table of results and tells you which library "wins."

I'm not going to do that, on purpose.

If I freeze the numbers into this article, it becomes exactly the thing that sent me down this road in the first place: an outdated benchmark. In six months the versions will have moved, .NET will have a new release, and a screenshot from today would be quietly lying to whoever finds this post later.

So instead of conclusions, here's the live data, always current:

benchmarks.jagoba.dev/dotnet-mappers

Open it, pick the scenario that matches your workload, and read today's results instead of mine from whenever you happen to read this.

Try it / steal it

Live benchmarks: benchmarks.jagoba.dev/dotnet-mappers
Benchmark runner: github.com/jagobainda/DotnetMappingBenchmarks
The website: github.com/jagobainda/dotnet-mapping-benchmarks-web

If AutoMapper's licensing change or the CVE has you reconsidering your mapping layer, I hope this saves you the afternoon of benchmarking I had to do. And if you spot a scenario worth adding, the runner is open source, PRs welcome.

What did you migrate to? I'm curious whether others landed on Mapperly, Mapster, or just went manual.

Sources: AutoMapper commercial editions announcement · GHSA-rvv3-g6hj-g44x / CVE-2026-32933