If you search for this comparison you will find benchmarks. Bundle size, time to interactive, rendering throughput. For a public e-commerce site those numbers matter enormously, because a slow page is lost revenue.
For an internal business application used by forty staff who have it open all day, they matter almost not at all. A 1.5 MB initial download is a one-time cost on a corporate network at nine in the morning. What matters instead is whether you can still staff, change, and afford this application in year three.
So here is the comparison framed around that instead.
What each one is genuinely good at
Blazor's real advantage is one language and one type system across the whole stack. Your validation rules, your domain models, and your business logic exist once, in C#, shared between server and UI. There is no DTO layer that drifts, no TypeScript interface that quietly stops matching the API response, no second implementation of the same rule that disagrees with the first. For a data-entry-heavy internal app, this eliminates an entire category of bug.
React's real advantage is the ecosystem and the hiring market. Whatever component you need — a virtualised grid, a scheduler, a rich text editor, a chart — several mature options exist and someone has already hit your edge case on Stack Overflow. And when your developer leaves, you can replace them from a far larger pool, at more predictable cost.
Both of those are real. Neither is a tiebreaker on its own.
The five questions that actually decide it
1. What does your team already know?
This dominates everything else, and teams routinely discount it because it feels like an admission rather than a strategy. A team of four C# developers building their first React application will produce a worse React app than they would have produced a Blazor app, for eighteen months, while they learn. That is not a knock on React. It is how learning works.
If your team is .NET and your app is internal, Blazor starts well ahead. If you already have React developers, the reverse holds just as firmly.
2. Who is going to maintain it in three years?
Ask this before you write a line of code. If the answer is "our in-house .NET team", Blazor keeps the application inside their existing skill set. If the answer is "we will hire a contractor when something breaks", the hiring market matters more than the developer experience, and React is easier and cheaper to hire for in most cities.
An application nobody can be found to maintain is an expensive application regardless of how elegantly it was built.
3. How network-tolerant does it need to be?
This is the question that eliminates Blazor Server outright in some environments, and it is worth being blunt about. Blazor Server keeps a persistent SignalR connection and round-trips UI events to the server. On a stable LAN or a good office connection, it is genuinely excellent — instant startup, no API layer to build, full server capabilities available directly.
On flaky mobile connections, high-latency links, or for field staff on patchy 4G, users will see the reconnection banner and they will hate it. If a meaningful share of your users are remote on poor connections, Blazor Server is off the table — and you are choosing between Blazor WebAssembly and React, which is a much closer contest.
4. How unusual is the UI?
If your application is forms, tables, filters, and dashboards — which describes the overwhelming majority of internal business software — both frameworks handle it comfortably, and commercial component vendors like Syncfusion and Telerik ship near-equivalent suites for both.
If you need something genuinely unusual — a custom canvas interaction, a specialised visualisation, a drag-and-drop designer — React's ecosystem depth becomes a real advantage. You will find a library. In Blazor you may end up wrapping a JavaScript one anyway, at which point you have both stacks and neither advantage.
5. Does anything else need this API?
If a mobile app, a partner integration, or a second front end will eventually consume the same backend, you need a real API regardless. That erases one of Blazor Server's main savings — not needing an API layer — and pushes the decision toward whichever front end your team prefers, since you are paying for the API either way.
The fork inside the fork: Server or WebAssembly
"Blazor" is two different products with different trade-offs, and conflating them is the most common mistake in these discussions.
Blazor Server runs your components on the server and pipes UI diffs over SignalR. Instant startup, no separate API needed, direct database access from component code, and your code never leaves the server. Costs: a persistent connection per user, server memory that scales with concurrent users, and total dependence on connection quality.
Blazor WebAssembly ships the .NET runtime to the browser and runs entirely client-side. Works offline, scales like static hosting, no per-user server state. Costs: a larger initial download, a real API layer you have to build and secure, and no direct database access.
.NET 8 and later let you mix render modes per component, which is genuinely useful — but treat that as an optimisation, not a strategy. Pick a primary mode based on the connection question above.
Where each one hurts in year two
Every technology choice has a delayed cost. These are the ones I see actually arrive.
Blazor, eighteen months in: you need a component nobody has built, and you end up writing JavaScript interop anyway — so you have a C# codebase with JavaScript pockets and developers who need both. Debugging across the interop boundary is genuinely unpleasant. And for Blazor Server specifically, concurrency growth turns into server cost in a way that surprises people who budgeted like it was a static site.
React, eighteen months in: dependency drift. The scheduling library is unmaintained, the build tooling has moved on, and a routine upgrade takes a week. Plus the quiet duplication tax — validation rules written in C# on the server and again in TypeScript on the client, which is fine until the day they disagree and nobody notices for a month.
Neither list should decide anything on its own. But you should choose knowing which of these two futures you would rather manage.
The shared-logic argument, concretely
The strongest technical case for Blazor on a business app is worth seeing rather than describing. A validation rule defined once, enforced identically on both sides:
// Shared class library — referenced by BOTH the server and the Blazor UI.
// One definition. No TypeScript mirror to drift out of sync.
public class MatterRequest
{
[Required, StringLength(120)]
public string ClientName { get; set; } = "";
[Required, RegularExpression(@"^[A-Z]{2}-\d{6}$",
ErrorMessage = "Reference must look like AB-123456")]
public string Reference { get; set; } = "";
[Range(0, 500_000)]
public decimal EstimatedValue { get; set; }
}The Blazor form and the API endpoint both validate against that one class. In a React setup the same rules typically exist twice — once in C# for the API, once in Zod or Yup for the form — and staying in sync is a discipline rather than a guarantee. Tools like NSwag narrow that gap by generating TypeScript clients from your API, and if you go the React route you should use one. But generated types cover shapes, not business rules.
So what would I actually recommend?
For an internal line-of-business application, built by a .NET team, used by staff on a reliable connection, that is mostly forms and tables and reports: Blazor, and Blazor Server unless the connection question rules it out. The shared-logic benefit is real, the ecosystem gap does not bite on this kind of UI, and the app stays inside your team's existing skills.
If any of those conditions break — remote users on poor connections, no in-house .NET team, an unusual interface, or an API that other clients will consume — the case narrows quickly and React becomes the safer long-term choice.
And there is a third answer people forget: use both, in different places. A Blazor admin panel for internal staff and a React customer portal is a perfectly sensible architecture when the two audiences have genuinely different needs. The cost of running two front ends is real, but it is smaller than the cost of forcing one stack to do a job it is bad at.
The cost difference, honestly
For a comparable internal application, initial build cost between the two is closer than vendors on either side will tell you — typically within fifteen percent, and dominated by scope rather than framework.
Where the numbers genuinely diverge is maintenance. A Blazor app maintained by an existing .NET team costs very little incremental effort, because it is the same people and the same skills. A React app maintained by contractors you hire per incident costs more per change but carries less key-person risk. Which of those is cheaper depends entirely on your organisation, not on the frameworks.
If you're making this call on a real project and want it pressure-tested by someone who has shipped both, send me the outline — team, users, connection, UI complexity — and I'll give you a straight recommendation. You can also get a build ballpark from the free cost estimator.