This page compares two sources for Polymarket and prediction-market historical data. PolymarketData.co runs a continuous API and S3 export service covering minute-level Polymarket data across 1M+ markets from August 2025 onward, with a free tier and three paid self-serve tiers plus a custom Enterprise plan. ZenHodl sells downloadable, one-time-purchase archives for Polymarket and Kalshi, with capture-time game-state fields on its Kalshi-side data and a free sample catalog. Pick PolymarketData.co for broad, continuously updated Polymarket history over a subscription API. Pick ZenHodl for Kalshi coverage, Kalshi depth and trade-print history, or file ownership without a recurring subscription.
At a Glance
| Item | ZenHodl | PolymarketData.co |
|---|---|---|
| Venues | Polymarket + Kalshi [1] | Polymarket only [2] |
| Time depth | Fixed archive windows (e.g. Dec 2025–Jan 2026 for the flagship archive); newest Kalshi slices run through Sep 2026 [3][4] | August 2025 onward, continuously updated [2] |
| Resolution | Kalshi depth: polled, top-150-by-volume markets, ~31s cadence through Jul 11 2026, ~42–47s after — not a full-exchange census. Trade prints: one row per executed trade [5] | 1-minute time series on paid tiers; 10-minute granularity, 10 requests/min on the free tier; no tick-level data [6] |
| Market coverage | 136M rows on the flagship Polymarket+Kalshi archive; 572.5M rows on the Kalshi Microstructure Tape; per-sport Kalshi slices also available [1][3] | 1M+ unique markets; 19B+ rows across series, events, and markets [2] |
| Pricing | One-time archives $9–$199; $39 per-sport Kalshi slices; API subscription Free/$49/$149/$499 per month [4][1] | Free $0/mo; Trader $60/mo ($540/yr); Pro $120/mo ($1,080/yr); Ultra $360/mo ($3,240/yr); Enterprise custom — 25% off annual billing [6] |
| Free tier | Free Developer API tier (500 req/mo, 5-min delay); free preview sample catalog [1][7] | Free plan: 10 req/min, 10-minute granularity, last month of data only, no historical order books [6] |
| Order-book depth | L1/L2 history with bid/ask + size; Kalshi side is a top-150-by-volume subset, not a full census [1][5] | Full order-book history with bid/ask depth [2] |
| Game-state / score sync | Present on Kalshi-side rows only, capture-time (not event-time). The flagship archive's Polymarket rows carry no game state [1][5] | Not stated anywhere on the public site [2] |
| Format | Parquet archives in ZIP, CSV free samples [1][7] | REST API + Python SDK; S3 exports in Parquet, CSV, or JSON [2] |
| Access model | One-time archive purchase; separate monthly API subscription [1][4] | Subscription-only via API/S3; no one-time ownership option stated [6] |
| Citation | Free MLB matched-book sample is DOI-minted on Zenodo (10.5281/zenodo.20816908), CC BY-NC 4.0 [8] | No DOI found on the public site; links to a separate "Academic Research" page [2] |
When to Pick PolymarketData.co
- You need broader Polymarket coverage: 1M+ markets and 19B+ rows from August 2025 onward, continuously updated [2].
- You prefer a continuous REST API or S3 exports with a Python SDK over downloading fixed archive files [2].
- You need 1-minute resolution across politics, crypto, weather, sports, and economic-indicator markets with relational metadata [2].
- You want a no-cost way to try the data first — the free plan gives 10-minute granularity and the last month of data [6].
- You want custom exports with time/category filtering for batch workflows [2].
When to Pick ZenHodl
- You need Kalshi data: the Kalshi Microstructure Tape or the $39 sport-specific Kalshi slices [3].
- You need Kalshi-side rows with a capture-time game-state field, or (for MLB) cross-venue rows joined to score, period, and clock at capture time [5][9].
- You prefer one-time purchases and file ownership over a recurring subscription [1].
- You want free preview samples before buying — small CSV extracts for offline inspection [7].
- You want a DOI-minted, citable sample dataset for academic work [8].
The Key Differences
1. Resolution: minute-level API vs polled Kalshi depth plus per-trade prints
PolymarketData.co offers 1-minute resolution on paid tiers (10-minute on the free tier), with no tick-level data stated [6]. ZenHodl's Kalshi depth is captured by polling a top-150-by-volume subset of markets at a measured cadence of roughly 31 seconds before Jul 12, 2026 and 42–47 seconds after — not continuous or tick-level, and not every market is covered on every cycle [5]. ZenHodl's trade prints are one row per executed trade. If predictable-cadence Polymarket history is your need, PolymarketData.co is the more direct fit. If you need Kalshi depth or executed-trade history, ZenHodl is the only one of the two that offers Kalshi data at all, with coverage limits disclosed rather than claimed as complete.
2. Market breadth vs venue-specific depth
PolymarketData.co covers 1M+ Polymarket markets and 19B+ rows since August 2025, continuously updated, spanning many event categories [2]. ZenHodl covers fixed, disclosed archive windows across both Polymarket and Kalshi, with specialized Kalshi sport slices and an explicit top-150-by-volume disclosure on its Kalshi depth [1][5]. Researchers needing very broad, continuously updated Polymarket coverage should look at PolymarketData.co; researchers needing two-venue matched coverage or Kalshi microstructure — coverage limits factored in — should look at ZenHodl.
3. Game-state tagging and ownership model
ZenHodl's Kalshi-side archives and its MLB cross-venue product attach a capture-time game-state field to rows, but this is capture-time, not exact event-time, and it applies only to the Kalshi side — the base Polymarket+Kalshi archive's Polymarket rows carry no such field [1][5]. PolymarketData.co's public pages state no score or game-state sync [2]. Separately, ZenHodl archives are one-time purchases you download, while its API product is a monthly subscription [1][4]. PolymarketData.co offers only recurring subscription tiers through API or S3 exports [6].
Free Sample & Next Steps
ZenHodl publishes small free preview samples for each archive — a Kalshi orderbook sample, a per-sport Polymarket CLOB depth sample, and a Kalshi burst sample spanning several leagues — so you can inspect the schema before buying [7]. ZenHodl also publishes one free, DOI-minted, CC BY-NC 4.0 sample on Zenodo: a single completed MLB matchup with tick-by-tick aligned Polymarket/Kalshi prices and the winner labeled, linked from ZenHodl's samples page [8]. Full archive options: zenhodl.net/products and zenhodl.net/pricing.
For Research & Citation
ZenHodl's free single-game MLB Cross-Venue Matched Book sample is DOI-backed via Zenodo (10.5281/zenodo.20816908, CC BY-NC 4.0) and linked from the samples page [8]. PolymarketData.co does not list a DOI for citation on its public pages, though it links to a separate "Academic Research" page [2].
Sources (checked 2026-09-25)
- zenhodl.net/products — ZenHodl archive catalog, prices, row counts
- polymarketdata.co — competitor homepage: coverage, format, venues
- zenhodl.net/kalshi-historical-data — Kalshi archive methodology and honest-limits disclosure
- zenhodl.net/pricing — ZenHodl API subscription tiers
- zenhodl.net/.well-known/data-products.json — machine-readable product/price/row-count feed
- polymarketdata.co/pricing — competitor plan tiers, prices, and rate limits (re-fetched 2026-09-25; Free $0, Trader $60/mo, Pro $120/mo, Ultra $360/mo, 25% off yearly, confirmed unchanged)
- zenhodl.net/samples — ZenHodl free sample catalog
- doi.org/10.5281/zenodo.20816908 — Zenodo record for the free MLB matched-book sample
- zenhodl.net/products/mlb_matched_archive — MLB Cross-Venue Matched Book product page