Version: Next

Changelog

For release notes of previous versions, please check the Releases page in RestSharp GitHub repository.

Changes between major versions are documented in the documentation for each version on this website.

v114.1

TrailingHeaders on RestResponse — HTTP response trailers (RFC 9110 trailer fields) are now exposed as a separate TrailingHeaders collection, kept apart from Headers and ContentHeaders. Trailers are populated on .NET 8 and later after the response content has been read; on .NET Framework and .NET Standard the collection is always empty. (#2414)

Default serializers are registered lazily — RestClient no longer instantiates the built-in System.Text.Json serializer before the configureSerialization callback runs. Replacing the JSON serializer (for example with UseNewtonsoftJson()) now avoids loading System.Text.Json at all, which fixes assembly binding failures in .NET Framework plugin scenarios. (#2403)
Synchronous Execute methods run on the thread pool — the sync-over-async bridge now uses Task.Run and GetAwaiter().GetResult() instead of a custom synchronization context, preventing deadlocks when calling the synchronous API from a UI or ASP.NET synchronization context. (#2371)

Fix AddObjectStatic throwing NullReferenceException when any property of the object is null. Null properties are now skipped, consistent with AddObject. (#2401)

IAuthenticator interface signature changed — Authenticate now accepts an optional CancellationToken parameter. All custom authenticator implementations must be recompiled. (#2362)
FollowRedirects and MaxRedirects removed from ReadOnlyRestClientOptions — these properties are now excluded from the generated immutable wrapper. Use RedirectOptions instead. Code accessing these properties on ReadOnlyRestClientOptions must be updated. (#2360)
Extension method signatures changed — AddParameter<T>, AddOrUpdateParameter<T>, AddHeader<T>, AddOrUpdateHeader<T>, AddQueryParameter<T>, and AddUrlSegment<T> now have an additional optional CultureInfo? culture parameter. Assemblies compiled against v113 must be recompiled. (#2354)

OAuth2 token lifecycle authenticators — new OAuth2ClientCredentialsAuthenticator, OAuth2RefreshTokenAuthenticator, and OAuth2TokenAuthenticator that handle obtaining, caching, and refreshing tokens automatically. (#2362)
Custom redirect handling with RedirectOptions — RestSharp now manages redirects internally instead of delegating to HttpClient, fixing lost Set-Cookie headers on redirects. New RedirectOptions class provides fine-grained control over redirect behavior. (#2360)
MergedParameters on RestResponse — provides a combined view of request and default parameters at execution time, useful for logging and debugging. (#2349)
Restored AddCookie(name, value) overload — the simple two-parameter form defers domain resolution to execution time. (#2351)

MultipartFormQuoteParameters now defaults to true — multipart form parameter names are now quoted per RFC 7578. (#2357)
InvariantCulture used for parameter formatting — all generic parameter methods now format values using CultureInfo.InvariantCulture by default. Pass a CultureInfo explicitly if locale-specific formatting is needed. (#2354)
Improved ErrorMessage for timeouts — now shows "The request timed out." instead of "A task was canceled.". (#2356)
ErrorMessage surfaces root cause — uses GetBaseException().Message to show the actual error instead of generic wrapper messages. (#2352)
HttpClient.DefaultRequestHeaders no longer modified — Expect100Continue is now set per-request. Safe to share an HttpClient across multiple RestClient instances. (#2363)

Fix ConfigureAwait(false) missing on several await calls, preventing deadlocks in sync-over-async scenarios. (#2367)
Fix ResponseUri returning original URL instead of redirect target when FollowRedirects=false. (#2350)
Fix default parameter merging bugs (multi-value dedup, request mutation, BuildUriString without execute). (#2349)
Fix OAuth1 double-encoding of RFC 3986 special characters in URL paths. (#2341)
Fix pipe character encoding when AddQueryParameter is used with encode=false. (#2345)
Fix XmlDeserializer when XML uses same tag name in nested elements. (#2339)
Fix credential/UseDefaultCredentials property order on HttpClientHandler. (#2353)
Fix URL escaping on .NET Framework 4.6.2. (#2327)