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If a catcher received 260 test events but showed only the latest 100, the first 160 may have been evicted—but that arithmetic alone does not prove FIFO eviction caused the loss. Treat the catcher as an inspection window until you verify its capacity and overflow behavior, then compare every event ID sent with every ID captured. A missing ID should fail the test, not disappear into a scrolling inbox.
What the 160 missing events do—and do not—tell you
The reported numbers imply a 100-event retained window: 260 arrivals minus 160 missing leaves 100. That conclusion holds only if each event arrived once and there were no duplicate deliveries, retries, or other losses. The specific catcher’s buffer size and eviction policy are not established by the count alone.
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A bounded buffer may keep recent events and remove older ones when full, but other implementations reject new events, block senders, or drop data without an obvious warning. Inspect the catcher’s configuration, overflow code, and logs before labeling the incident FIFO eviction. FIFO means first in, first out: when a full buffer removes its oldest item to make room for a new one, the earliest events vanish first.
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How to prove which events are missing
Give every event a unique identity
Add both a unique event ID and a monotonic sequence number to each test payload. For example, a run might emit IDs such as run-2026-10-05-001 through run-2026-10-05-260, with a separate sequence field from 1 to 260. Save the sent ID list at the sender; do not depend on the catcher as the only record of what was emitted.
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Compare sent and captured sets
Retrieve or export the captured records, then compare the sender’s list with the receiver’s list as sets and as counts. Report the absent IDs, duplicates, and any unexpected IDs. Check timestamps and ordering as well: a retry or delayed delivery can make the first and last visible records misleading. If the sender recorded 260 unique IDs and the catcher has only 100 unique IDs, the comparison identifies the exact 160 missing events without assuming why they are missing.
Turn loss into a test failure
Assert that the captured unique-ID count equals the expected count and that every expected ID is present. Make overflow observable with an explicit error or counter. A test should fail if the catcher reports capacity reached or if any ID is absent, rather than passing because the events that remain look correct.
Reproduce and isolate the overflow behavior
- Start with a small numbered run. Send a sequence below the suspected capacity and confirm that the sender and catcher agree on the IDs.
- Increase the run beyond the suspected capacity. Keep the same ID and sequence fields, and preserve the sender’s emitted-ID list.
- Inspect the catcher. Find its configured capacity and overflow handling. Determine whether it rejects new entries, overwrites the oldest, blocks producers, or drops events silently; use logs or counters where available.
- Check for alternate explanations. Compare retries, duplicates, timestamps, and sender-side failures before attributing all missing IDs to eviction.
- Change one retention or persistence setting and repeat. Compare the emitted and captured ID sets again. Report only behavior observed in that implementation and configuration.
Why a webhook inbox may not be a test-run archive
Capture tools can impose different limits at different stages. An acceptance limit controls whether a new request is taken at all; a history limit controls how many already accepted requests remain visible. A rate limit controls request throughput, not stored history. These behaviors are not interchangeable, and a vendor’s limits do not establish the capacity of a separate in-memory catcher.
For examples checked on October 5, 2026, Webhook.site’s FAQ says free URLs stop accepting new requests after 100 requests or emails, while subscribed URLs expose the latest 10,000 and rotate or purge older requests periodically. The free limit is an acceptance cap, not evidence of FIFO eviction. The FAQ’s terms are vendor claims and can change; check the current Webhook.site FAQ for the account and URL you plan to use.
RequestBin’s documentation, checked October 5, 2026, lists the latest 100 requests per bin for its Free plan and unlimited history for its listed Pro and Team tiers. Those are plan-specific vendor terms, not a general property of webhook catchers. Confirm current details in RequestBin’s documentation.
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- Ideal for business energy measurement - In commercial buildings, it helps monitor energy usage across floors or departments allowing accurate cost allocation and identification of energy wastage. In manufacturing plants it tracks energy consumption of heavy machinery, optimizing usage to reduce operational costs. For store owners it monitors energy usage of systems like lighting, HVAC § refrigeration, helping to identify inefficiencies § reduce energy bills while supporting sustainable practices
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Webhook.site’s API documentation, last updated May 7, 2026, describes a dynamic rate limit of 100 divided by timeout seconds—up to 100 requests per minute at a one-second timeout. That documented API rate limit is separate from request-history capacity. The API also documents sorting, pagination, filters, retrieval of individual requests, and CSV export with a maximum export size; check Webhook.site’s API documentation for current limits and retrieval details.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Choose a capture path that preserves the evidence you need
For a small debugging run, an inbox can be convenient. For a burst that may exceed its visible history, use pagination or export before the records roll over, or forward important events into storage designed to retain them. Check the exact plan, acceptance limit, history cap, retention duration, and export limit on the day of the test; do not assume that a page showing recent requests contains the whole run.
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Webhook.site also describes queued asynchronous Custom Actions, which can run after an inbound request is processed. An action queue is a workflow feature, not a guarantee that inbound requests are durably stored. For self-hosting, the Webhook.site GitHub repository describes the project as a webhook and HTTP request testing and debugging tool and identifies its self-hosted open-source version; self-hosting still requires you to configure and operate durable storage if you need an audit trail.
Quick Recap
Prevent the next silent loss
- Keep an independent sender-side record of expected event IDs and count.
- Make the receiver test assert completeness, uniqueness, and expected count.
- Emit a visible overflow error or metric whenever the catcher reaches capacity.
- Page through or export captures before a count-based history limit can remove evidence.
- For important or large test runs, persist events outside a transient in-memory or browser-session inbox.
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