How is client-to-server clock skew calculated?

It uses an NTP-style midpoint estimation comparing the server's response Date header against the local timestamp recorded at request transmission and receipt.

Which authentication timestamp formats and headers are inspected?

It inspects AWS SigV4 (X-Amz-Date / Date), Azure REST headers (x-ms-date), generic X-Timestamp headers, and JWT payload claims (iat, nbf, exp).

Can JWT tokens be modified during live replay?

No. JWT claims are cryptographically signed, so modifying timestamps on the wire invalidates the token signature unless re-signed by the issuer.

What is the standard AWS SigV4 clock skew tolerance limit?

AWS SigV4 allows a maximum drift of ±15 minutes (900 seconds) between the request timestamp and the server's authoritative clock.

What is the difference between analyze and replay modes?

Analyze mode computes skew and inspects claims entirely offline, while replay mode sends active HTTP requests across specified ±skew second offsets.

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Request Replay & Clock Skew Correction for Distributed Systems

Parse a raw HTTP request or curl command, estimate client↔server clock skew from the response Date header (NTP-style midpoint formula), inspect timestamp credentials (X-Amz-Date, x-ms-date, X-Timestamp, JWT iat/nbf), replay with ±skew offsets and diff the results against real tolerance windows (AWS SigV4 ±15 min, Azure, OAuth, JWT leeway).

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2 examples

SigV4 request, offline skew diagnosis

A captured POST whose X-Amz-Date says 00:00:00 while the server's Date header said 00:16:00 and the local clock read 00:00:10 at receipt — a +950 s skew that blows past the ±15 min SigV4 window, with a corrected curl that advances the timestamp header to server time (00:15:50).

<section>parsed request card (POST api.example.com/v1/orders, SigV4 credential detected) · skew panel +950 s with the [949, 951] s Date-quantization interval · tolerance table: AWS SigV4 exceeded (950 > 900) · corrected curl advancing X-Amz-Date to 20260101T001550Z · signed-header warning</section>

curl import with a future-dated JWT

A curl command with a Bearer token whose nbf/iat claims decode without verification — the report shows the token was minted into the future relative to this clock, explains that JWT claims live inside the signature, and keeps the replay plan offline.

<section>curl parse card (GET https://tasks.example.com/api/queue, Basic-free, Authorization Bearer) · JWT panel: iat/nbf/exp decoded as NumericDates with deltas vs the local clock · X-Timestamp read as epoch seconds · tolerance table for JWT leeway · note that claims cannot be shifted on the wire</section>

Inputs

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6 options

ContentPaste or type the main input values.4

Raw HTTP request or curl commandtextareaRequiredCaptured response Date header (analyze)textOptionalLocal clock when it arrived (analyze)textOptionalReplay offsets in seconds (empty = auto)textOptional

SettingsAdjust formats, ranges, numbers, and modes.2

ModeselectRequiredTimeout per request (ms)numberOptional

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Request Replay & Clock Skew Correction for Distributed Systems

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Examples

1. AWS SigV4 RequestTimeTooSkewed Diagnosis

2. Premature JWT Activation Inspection

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