openappindex/app-store-de

openAPPindex — German iOS App Store: cooking and sleep categories

An open dataset of dated facts about two categories of apps on the German iOS App Store: which apps exist in the category, which of them the store's own search returns, and what Apple publishes about their prices and in-app purchases.

It is the data behind the working paper Search Without Recall: Preliminary Evidence on Discovery Failure and Price Opacity in a Mobile Application Market (Tim Meyerdierks, draft v0.1, September 2026) — openappindex.org/paper.html.

• Website and method: openappindex.org · method page
• Code (AGPL-3.0) and the authoritative copy of the data: github.com/tim-muky/openappindex
• DOI: PLACEHOLDER — Zenodo concept DOI, added after the first GitHub release

What the data says, as published by the project

These figures are copied from the project's README and findings; they are reproducible from the scripts in the repository.

	Cooking	Sleep & meditation
Apps in the classified category	941 (≥991 incl. price-unverified)	3,578
Absent from the single obvious query	81% (579 of 715)	88% (1,013 of 1,155)
Reachable only via the similar-apps graph	28% (276 of ≥991)	68% (2,423 of 3,578)
Listed "free"	96% (907 of 941)	96% (3,417 of 3,578)
…of those, charging in-app	77% (697 of 907)	77% (2,581 of 3,351)
Median highest in-app purchase	€39.99	€39.99
Largest single in-app purchase	€599.99	€1,199.99

Rules the data follows

• Facts only. Names, developers, categories, versions, dates, listed prices, rating counts, and Apple's published in-app purchase lists. There are no scores, grades or labels.
• No descriptions, no review text. App descriptions and release-note text are the copyright of their developers and are deliberately excluded. Only derived measurements are kept: description_length, release_notes_present, release_notes_length. No review text is included. Regenerate the full records locally with the repository's scripts if you need them.
• Missing is missing, never zero. A value that was not collected is null (or, in the sweep and closure files, the key is absent because Apple did not return it). It is never filled with 0, an empty list, or an estimate. See Reading missing values below.
• No annualised prices. Apple does not publish billing periods reliably. An in-app purchase is recorded with the name and price Apple lists, including the developer's own label (for example Jahresabo); it is never converted to a per-year or per-month figure. "Highest in-app purchase" always means the highest single listed item.
• Every record is dated. Each record carries the date or timestamp it was read; a fact without its read date should not be quoted.

Read dates

• Cooking: measured 19 August to 1 September 2026. Price records carry their own read_at timestamp. Weekly snapshots in cooking/snapshots/ are named by their read date (2026-08-23, 2026-09-17) and each app record carries its own read date.
• Sleep and meditation: measured 1–2 September 2026.

Files and subsets

All files are JSON, UTF-8. Prices are strings exactly as Apple displays them on the German storefront (for example "14,99 €", "Gratis"); they are not parsed into numbers here.

Cooking (cooking/, from sample/data/public/ in the repository)

Subset / file	One row is	Notes
cooking_sweep — corpus_de.json	an app returned by the 25-query search sweep (iTunes Search API, storefront de)	The rows are under the apps key; the 25 queries are in queries. This is the unclassified sweep output (1,312 apps per the project's docs): it still contains apps that are not cooking apps, such as pharmacy apps matched by Rezept. Category membership is decided by sample/classify.py in the repository, not by a column here.
cooking_closure — closure_apps.json	an app reached by walking the store's own "similar apps" graph	Same fields as the sweep.
cooking_prices — prices_de.json	one read of an app's product page	track_id, read_at, read_ok, subtitle, in_app_purchases (list of {name, price}).
corrections — corrections.json	a dated correction to the project's own data	German text, with a link to the method page.
cooking/snapshots/<date>.json (files only, no viewer subset)	a dated snapshot of the apps served by the index	Object keyed by app id; abbreviated fields (n name, dev developer, v version, upd last update, rel release, price, notes/notes_len, iap_n/iap_min/iap_max, read, iap_read). collected states which parts were read for that snapshot.
cooking/changelog/<ISO week>.json (files only)	one week's diff between two snapshots	New, gone, updated, price changes, corrections; every line dated.

Main fields in the sweep and closure files (Apple's iTunes Search API names): trackId, trackName, sellerName, artistId, primaryGenreName, genres, version, releaseDate, currentVersionReleaseDate, formattedPrice, averageUserRating, userRatingCount, languageCodesISO2A, trackViewUrl, plus the derived description_length, release_notes_present, release_notes_length.

Sleep and meditation (sleep/)

3,578 apps, measured 1–2 September 2026, exported by sleep/export_public.py; every headline figure is recomputed from these two files by sleep/verify_public.py.

• sleep_category — category_sleep_de.json: one record per app in the final (v3) category, with the Lookup API fields, text-length measurements, found_via (query_sweep with every query and result position, or similar_apps_graph with the hop number and the app it was first reached from) and classification.
• sleep_prices — prices_sleep_de.json: one product-page read per app — read_at, read_ok, and in_app_purchases (name and price exactly as Apple shows them). read_ok: false means not collected; read_ok: true with in_app_purchases: null means the page showed no list.

An app counts as charging in-app when at least one listed item is priced above €0 (two sleep apps list only €0.00 items).

Not included here

The citation-experiment records (gate_*.json, perplexity_retrieval_probe_*.json) stay in the GitHub repository and the Zenodo archive. They describe assistant answers, not apps.

Reading missing values

Where	Value	Meaning
prices_de.json	read_ok: false, in_app_purchases: null	The product page was not read. Nothing is known.
prices_de.json	read_ok: true, in_app_purchases: null	The page was read and carried no in-app purchase list on that date.
prices_de.json	read_ok: true, in_app_purchases: [...]	The list as Apple published it on that date (see truncation below).
sweep / closure files	key absent	Apple's API did not return that field.
sweep / closure, loaded with datasets	null	The same absent key; the loader fills it with null.
averageUserRating	0 with userRatingCount: 0	Apple's own value for an app with no ratings. Read it as "no ratings", not as a rating of zero.
snapshots	iap_n, iap_min, iap_max, iap_read = null	In-app purchases not collected for that app in that snapshot.

Known limitations

• Two categories, one storefront. Cooking and sleep/meditation, German iOS App Store only, one platform, a short window. Nothing here describes other categories, other countries, or Google Play.
• Keyword classifier. Category membership is decided by a keyword classifier. German homonyms broke it repeatedly — Rezept is both recipe and medical prescription; Kochen and Backen match cooking games; wickel hides inside entwickelt, slim inside Muslim. Each trap was fixed when found and every correction is published with its date (corrections.json, and the README's "Errors we made, and published").
• Apple truncates in-app purchase lists at 10 items. Product pages list at most ten in-app purchases: 203 of 1,265 price records sit at exactly ten, with none above. Where an app's list sits at ten, the highest in-app purchase recorded here is a lower bound.
• What Apple publishes is what we have. Apple does not publish billing periods reliably, so none are inferred.

Corrections

If something here is wrong — particularly if you build an app that appears in the data — write to korrektur@openappindex.org. Every notice is checked and corrections are published with a date.

Licence and attribution

Data: CC BY 4.0. Attribution: openAPPindex — https://openappindex.org. The code that produces it is AGPL-3.0 and lives in the GitHub repository.

Citation

@techreport{meyerdierks2026searchwithoutrecall,
  author      = {Meyerdierks, Tim},
  title       = {Search Without Recall: Preliminary Evidence on Discovery Failure and Price
                 Opacity in a Mobile Application Market},
  institution = {The openAPPindex project},
  type        = {Working paper, draft v0.1},
  year        = {2026},
  month       = sep,
  url         = {https://openappindex.org/paper.html},
  note        = {DOI: PLACEHOLDER}
}