This page tracks how heavily Fastly (Nasdaq:FSLY) is being shorted: ORTEX's daily short interest estimate, the cost to borrow the shares, utilization of the lendable supply and days to cover, next to the official exchange-reported figure.

Short interest: The number of shares that have been sold short and not yet bought back, usually shown as a percentage of free float (the shares available to trade). ORTEX estimates it every day from securities-lending data, instead of waiting for exchange reports that are published only twice a month and about two weeks late.
Cost to borrow: The annualised fee a short seller pays to borrow the shares, as a percentage of the position's value. A rising cost to borrow means lendable shares are getting scarce and holding the short is getting more expensive.
Utilization: The share of the lendable supply of a stock that is currently on loan. Close to 100% means almost no shares are left to borrow.
Days to cover: Short interest divided by average daily trading volume: roughly how many days of normal trading it would take for every short seller to buy back their shares.
Exchange-reported short interest: The official figure published by the exchange or regulator (in the US, FINRA twice a month). It is accurate but delayed, which is the gap the ORTEX daily and intraday estimates fill.

Source: ORTEX. Some figures are limited on the free view; live data and full history are part of ORTEX Advanced.

FSLY key data

Fastly (Nasdaq: FSLY) has a market capitalization of $2.56B. Last close $15.85 (as of 2026-11-09); 52-week range $7.87 to $34.82. ORTEX data as of 2026-10-22: short interest was 13.64% of free float, 3.6 days to cover and the average cost to borrow was 0.46%. Sign up for live short interest data.

Fastly (FSLY) Short Interest

Nasdaq • FSLY • US31188V1008

15.85Last close

Market Closed

As of Oct 22, 2026, ORTEX estimated 13.6% of free float sold short, 3.6 days to cover, cost to borrow 0.46%. Sign up for live short interest data.

About this data: FSLY short interest, cost to borrow and days to cover

Short interest: The number of shares that have been sold short and not yet bought back, usually shown as a percentage of free float (the shares available to trade). ORTEX estimates it every day from securities-lending data, instead of waiting for exchange reports that are published only twice a month and about two weeks late.
Cost to borrow: The annualised fee a short seller pays to borrow the shares, as a percentage of the position's value. A rising cost to borrow means lendable shares are getting scarce and holding the short is getting more expensive.
Utilization: The share of the lendable supply of a stock that is currently on loan. Close to 100% means almost no shares are left to borrow.
Days to cover: Short interest divided by average daily trading volume: roughly how many days of normal trading it would take for every short seller to buy back their shares.
Exchange-reported short interest: The official figure published by the exchange or regulator (in the US, FINRA twice a month). It is accurate but delayed, which is the gap the ORTEX daily and intraday estimates fill.

Source: ORTEX. Some figures are limited on the free view; live data and full history are part of ORTEX Advanced.