Shared data

Shared props are merged into every page. A page prop with the same key wins.

Register shared values

builder.Services.AddInertia(o =>
{
    o.Share("appName", "Demo");                                      // static value
    o.Share("auth", ctx => new AuthInfo(ctx.User.Identity?.Name));   // per request
});

Share values from anywhere with an HttpContext, such as middleware or a handler:

app.Use((context, next) =>
{
    context.Inertia().Share("locale", CultureInfo.CurrentUICulture.Name);
    return next(context);
});

The value can be any prop, including another factory:

o.Share("permissions", ctx => Once(() => LoadPermissions(ctx)));
o.Share("plans", Once(() => plans.All()));   // like Laravel's shareOnce

plans is resolved once and kept by the client across visits.

The shared prop key list

The top-level shared keys are listed in the page object so the client can keep them across navigations:

{
  "props": { "errors": {}, "appName": "Demo", "auth": { "name": "Ada" } },
  "sharedProps": ["errors", "appName", "auth"]
}

errors is always shared, so the list always contains at least "errors". Turn the list off with:

builder.Services.AddInertia(o => o.ExposeSharedPropKeys = false);

When to use shared props

Use shared props for values that every page needs and that are cheap to compute:

• the signed-in user or tenant name
• the application name and locale
• feature flags
• a once-per-client value such as a plan catalogue

Keep large or page-specific data in page props. Shared props are considered on every page response, including partial reloads, so keep them cheap or wrap an expensive value in Once.

TypeScript

The generated declarations infer shared props from the values passed to o.Share(...). Factories and per-request shares are typed as unknown; use o.TypeScript.SharedProps<T>() when you want an explicit shape. See TypeScript types.