# What is the Skinory CS2 Index?

**Short answer:** The [Skinory CS2 Index](https://skinory.io/en/cs2-index) tracks daily price changes with base 100 at each category’s first snapshot. It combines the price ratios of matched items as a weighted arithmetic mean; weights are the previous-day price times listed quantity. Method version 2 takes the ratios from Skinport lowest listings; version 3 takes, for each item, the median ratio across the public markets that quoted it on both days. The API reports the version in use as methodVersion. It is an analytical indicator, not a tradeable investment or a price forecast.

[Skinory](https://skinory.io/en/about)

Published: 2026-10-17
Updated: 2026-11-10
Facts checked: 2026-11-10

[What is the Skinory CS2 Index?](https://skinory.io/en/cs2-answers/what-is-skinory-cs2-index)

## How a day is calculated

For each matched item the index computes a price ratio: today’s price divided by the previous snapshot price. In version 2 the price is the Skinport lowest listing. In version 3 the index takes the markets that quoted the item in both snapshots, divides today’s best offer by the previous one on each of them and uses the median of these ratios, so one market dropping out or one outlier quote does not move the item; the item’s listed value then counts listings on all its markets. Each item ratio is multiplied by the item’s previous listed value, the results are summed and divided by total matched weight, and the previous index level is multiplied by that weighted mean. The [methodology](https://skinory.io/en/methodology#index) shows the version in use, its markets and the actual eligibility thresholds.

For example, equal previous listed values and price changes of +10% and −20% give a mean ratio of (1.10 + 0.80) / 2 = 0.95, a 5% decline. This two-item example illustrates the arithmetic; actual categories require more matched items. Ratios outside the permitted range are excluded rather than clipped. Stale snapshots are skipped, and newly appearing items do not enter that day’s matched comparison.

## What it is for

The index answers the question "is the market up or down" with one dated number. Category sub-indexes, from knives and gloves to stickers, cases and charms, show which part of the market is moving. Weekly reports keep a permanent page per ISO week with the level, the change and the biggest movers, so a claim about the market can be cited with a date.

- The hub at [/cs2-index](https://skinory.io/en/cs2-index) shows the current level, 1, 7 and 30 day changes and every category.
- The [market hub](https://skinory.io/en/cs2-market) places the index next to the market cap, movers, arbitrage and deals.
- `GET /api/v1/index` and `GET /api/v1/index/history` expose index data as JSON. Skinory’s own derived indicators are available under CC BY 4.0; third-party raw prices and game assets retain their source rights. See the [developers page](https://skinory.io/en/developers).

## Limits

The index uses listing quotes, not completed trades. Versions 2 and 3 form one series without a reset; a switch between them is marked on the chart and returned by the API. Listed quantities can change and affect future weights; source coverage is incomplete, and version 3 leaves out items quoted on fewer markets than the methodology requires. Historical capitalization estimates before index launch are a separate series, not reconstructed index levels. Cite the category, snapshot date, data time and method version alongside a value.

## Questions and answers

### Why does the index differ from the market cap?

Capitalization includes observed quantities and an assumed supply coefficient. The index compares matched price ratios, but quantities affect eligibility and subsequent weights. If all eligible matched prices remain unchanged, their weighted ratio is 1; a listing count alone is not a price change.

### Can I cite the index in an article?

Yes. State Skinory, the snapshot date, category and comparison interval, and link to the index or relevant report. CC BY 4.0 applies to Skinory’s own derived indicators; it does not relicense third-party raw data.

### Why is a category missing a level?

A category needs a minimum number of matched items between two days. Small categories may skip days until enough fresh listings exist on both sides.

## Sources

- [Skinory methodology, index section](https://skinory.io/en/methodology)
- [Skinory CS2 Index](https://skinory.io/en/cs2-index)

## How to cite

What is the Skinory CS2 Index?. Skinory, updated 2026-11-10. https://skinory.io/en/cs2-answers/what-is-skinory-cs2-index

[CC BY 4.0](https://creativecommons.org/licenses/by/4.0/) — attribution to Skinory with a link to this page. [AI citation policy](https://skinory.io/ai-attribution.txt)