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  • Software and systems
  • HTTP service

100

HTTP 100 Continue: meaning and next diagnostic branch

Verified with sources2 sourcesReviewed Aug 23, 2026
Technician coming? See what they must show you

Risk level

Low

Usually safe to check without specialist tools.

Urgency

Medium

Quick answer

HTTP 100 Continue means: The initial request was received and the client can continue sending the request content. It identifies a protocol result, not the failed component. Preserve one request/response pair and discriminate the exact HTTP version, connection hop, Upgrade/Expect fields and whether an intermediary rewrote them.

Safety first

Stop and check this first

  • Do not downgrade transport security or disable protocol validation globally to make one request pass.

Safe checks you can perform

  • Freeze one complete failing exchange
  • Change one variable and repeat once
  • Stop before retries hide the first failure

Leave these tasks to a qualified professional

  • Do not attempt this professional task: Trace-led handoff for HTTP 100

What a technician must be able to justify

A technician is coming

These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.

These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.

  1. Trace-led handoff for HTTP 100

    What they doCorrelate wire-level protocol/version, connection reuse and intermediary transformations at every hop before changing TLS, HTTP/2/3 or proxy configuration.

Before accepting a part or repair

Nothing has been shown yet. Do not accept a part swap based on the code alone.

Checks and evidence, step by step

Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.

  1. 1

    Freeze one complete failing exchange

    No special tools

    Procedure

    Record HTTP 100, timestamp, method, scheme/host/path without secrets, response headers and body, request ID, client, deployment version and every proxy/CDN/gateway hop. Redact credentials and personal data.

    Do not downgrade transport security or disable protocol validation globally to make one request pass.

    Evidence: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semantics

  2. 2

    Change one variable and repeat once

    No special tools

    Procedure

    Compare the raw exchange at the client edge and origin once. Keep the same method and payload; change only the protocol/hop under test.

    Do not downgrade transport security or disable protocol validation globally to make one request pass.

    Evidence: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semantics

  3. 3

    Stop before retries hide the first failure

    No special tools

    Procedure

    A mismatch between hops isolates negotiation or intermediary behavior. Identical behavior at the origin belongs to server protocol support, not DNS or application data.

    Do not downgrade transport security or disable protocol validation globally to make one request pass.

    Evidence: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semantics

Where this code applies

A code is meaningful only inside the right product and version context.

Primary scope

System
Software and systems
Brand
HTTP
Product type
HTTP service

Known code variants

  • 100 Continua
  • 100 Continuar
  • 100 Continue
  • 100 Continuer
  • 100 Fortfahren
  • HTTP 100
  • HTTP status 100

What it means

Registered meaning: The initial request was received and the client can continue sending the request content. The next decision boundary is the exact HTTP version, connection hop, Upgrade/Expect fields and whether an intermediary rewrote them. Before changing infrastructure or buying support, require: Correlate wire-level protocol/version, connection reuse and intermediary transformations at every hop before changing TLS, HTTP/2/3 or proxy configuration.

Warnings and stop conditions

  • Lowsource verified

    Do not downgrade transport security or disable protocol validation globally to make one request pass.

    Evidence: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semantics

Symptoms and causes

Probable causes · in order

  • What the registered HTTP status establishesConfirmed

    IANA registers 100 as Continue. The controlling specification establishes: The initial request was received and the client can continue sending the request content.

    Evidence: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semantics

  • The evidence that changes the next branchPossible

    Capture the exact HTTP version, connection hop, Upgrade/Expect fields and whether an intermediary rewrote them. A mismatch between hops isolates negotiation or intermediary behavior. Identical behavior at the origin belongs to server protocol support, not DNS or application data.

    Evidence: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semantics

Virtual technician

Does 100 still appear after these checks?

Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.

Start diagnosis

Sources and technical references

  1. 1

    IANA HTTP Status Code Registry

    Internet Assigned Numbers Authority · 2025 · standard

  2. 2

    RFC 9110 - HTTP Semantics

    IETF / RFC Editor · 2022 · standard

Sources: IANA HTTP Status Code Registry · RFC 9110 - HTTP Semanticsreviewed 2026-08-23 · verified

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