What does the sandbox answer with?

It depends on the mode: Bid returns one bid per impression with a built-in creative (banner HTML, VAST 4.2, or Native 1.2 JSON) sized from banner.w/h, format[0] or video.w/h; No-bid returns 204 or 200 with an nbr reason; Random bids with the configured probability; Custom renders your own JSON template with macros; Timeout holds the connection for tmax + 500 ms and then returns 204.

Which macros work in custom templates?

{{id}}, {{imp.id}}, {{imp.w}}, {{imp.h}}, {{imp.kind}}, {{imp[n].any.path}}, {{uuid}}, {{timestamp}}, {{price}}, {{currency}}, {{seat}}, {{crid}}, {{cid}} and any top-level BidRequest path such as {{site.domain}} or {{device.ua}}. Unknown paths expand to an empty string. The expanded template must be valid JSON, otherwise the bidder answers 500 and records the error.

Can exchanges send gzip-compressed bid requests?

Yes. gzip, deflate and br request bodies are decoded transparently and the original encoding is shown on each request. Bodies are captured up to 256 KB; larger bodies are truncated and flagged.

Is the traffic private?

Only someone holding the endpoint URL can post to it, and only your browser holds the owner token needed to read the captured requests. Everything is ephemeral and disappears when the endpoint expires or you delete it. Do not send production user data.

RTB Bidder Sandbox

Get a personal OpenRTB 2.6 bidder URL in one click. Point any exchange test tool, Prebid Server, ad server QA harness or cURL at it and watch every BidRequest arrive live: impressions with type pills and sizes, tmax, site domain or app bundle, device type, geo, GDPR/GPP/COPPA flags, floors and the decision the sandbox made. Configure how it answers — always bid, always no-bid (204 or 200 + nbr), random fill with a bid rate, a custom JSON template with {{macros}}, or a deliberate timeout — and preview the exact response for any captured request before saving. Built-in creatives cover banner HTML, VAST 4.2 video/audio and Native 1.2 JSON, matched to each imp. gzip request bodies are accepted; invalid JSON is still recorded so you can see what the sender transmitted.

Live endpoint via the FizzKit relay — captured data auto-deletes after 1 h idle

Bidder endpointIdle

creating…

Your bidder is listening

Point any exchange test tool, Prebid Server, or a cURL at the URL above. Every POST is captured live and answered according to the bidder behaviour below (bid, no-bid, random fill, custom template, or a deliberate timeout).

gzip / deflate / br request bodies are accepted and decoded.
Bodies up to 256 KB are captured; larger bodies are truncated and flagged. The last 100 requests are kept.
Timeout mode holds the connection for tmax + 500 ms so you can test your exchange side.
Invalid JSON is still recorded (HTTP 400) so you can see what the sender actually transmitted.

fires the display-banner preset at your own endpoint

cURL

To test gzip, pipe the body through gzip -c and add -H 'content-encoding: gzip'.

Live capture — open fullscreen for a bigger request list and detail panel

Waiting for bid requests…

Select a request to inspect it.

Requests

QPS (60 s)

0.00

Bid rate

—

Avg tmax

—

Imp mix

—

Top domain / bundle

—

gzip share

—

Parse errors

Waiting for the endpoint…

OpenRTB Request Builder

Build OpenRTB 2.6 bid requests with a form or JSON, then send them to any bidder and inspect the response.

Bid Response Inspector

Decode an OpenRTB BidResponse: bids, macros, no-bid reasons, creative preview and win/billing notice firing.

OpenRTB Inspector

Validate & annotate OpenRTB 2.6 BidRequest and BidResponse JSON.

RTB & Ad Revenue Calculator

eCPM, CPC, CPA and CPV conversions, fill and revenue projections, rev-share chains, bid shading, auction clearing and budget pacing.

Request Bin

Get a unique URL that captures every webhook or HTTP request and shows it live — headers, body, query, raw wire format.

VAST Inspector

Fetch or paste VAST 2/3/4 tags — follow wrapper chains, validate, ping pixels, and play media files.

How to use RTB Bidder Sandbox

1Open the tool — a bidder URL is created for you; copy it or click "Send test bid request" to see a first capture.
2Point your exchange, Prebid Server adapter, QA harness or cURL at the URL with a POST body containing an OpenRTB BidRequest.
3Click any captured request to see its summary, schema validation, annotated fields, raw JSON and the response the sandbox sent.
4Open "Bidder behaviour" to pick a mode, price, creative overrides or a custom template; check the live preview, then save.

About RTB Bidder Sandbox

RTB Bidder Sandbox is part of FizzKit — a collection of focused developer and ad-tech tools. This tool gives you a live endpoint on the FizzKit relay; captured requests live in memory only and are deleted automatically after 60 minutes of inactivity (3 hours at most).

Frequently asked questions

Endpoints expire after 60 minutes of inactivity (3 hours at most); every captured request resets the idle timer. The sandbox is shared and has a small number of concurrent slots — if it is full you get a clear message to try again in a few minutes. The endpoint id and owner token are kept in your browser so a refresh reconnects to the same URL. Create a new one at any time.