Korro Bio, Inc. (KRRO)
Every FINRA and SEC series the site collects for Korro Bio, Inc.: short interest with days to cover, daily short sale volume, fails to deliver and Form 4 insider trades. Listed on Nasdaq.
1.5M
Short interest
settlement 2026-08-14
14.3
Days to cover
+5.1% vs prior
55.5%
Short share of volume
2026-09-11
3
Fails to deliver
settlement 2026-08-14
-$413K
Insider flow, 90 days
2 buys, 5 sells
As of 2026-09-11.
Short interest
FINRA, twice a month; the last 12 months shown, all 48 settlements in the JSONAs of 14 August 2026, short interest in KRRO is 1,511,713 shares, up 52,533 shares over the last month. Over the last 48 readings it ranged from 222,784 shares (30 September 2024) to 1,705,061 shares (30 June 2026). At the reported average volume of 106K shares a day that is 14.3 days to cover, a crowded short.
Embed this chartfree, with the attribution line it carries
<iframe src="https://xoomar.com/embed/stocks/krro" width="100%" height="440" style="border:0;max-width:100%" loading="lazy" title="XOOMAR chart"></iframe>
| Settlement | Shares short | Change | Avg daily volume | Days to cover |
|---|---|---|---|---|
| 2026-08-14 | 1,511,713 | +5.1% | 105,843 | 14.28 |
| 2026-07-31 | 1,438,506 | -1.4% | 157,016 | 9.16 |
| 2026-07-15 | 1,459,180 | -14.4% | 229,522 | 6.36 |
| 2026-06-30 | 1,705,061 | +29.2% | 367,177 | 4.64 |
| 2026-06-15 | 1,319,658 | +4.3% | 144,447 | 9.14 |
| 2026-05-29 | 1,265,439 | +5.9% | 166,458 | 7.60 |
| 2026-05-15 | 1,194,496 | +6.9% | 104,312 | 11.45 |
| 2026-04-30 | 1,117,429 | +3.0% | 71,061 | 15.72 |
| 2026-04-15 | 1,085,053 | +2.1% | 214,847 | 5.05 |
| 2026-03-31 | 1,062,337 | +4.3% | 204,575 | 5.19 |
| 2026-03-13 | 1,018,585 | -2.3% | 296,914 | 3.43 |
| 2026-02-27 | 1,042,910 | -2.2% | 142,049 | 7.34 |
| 2026-02-13 | 1,066,433 | -6.1% | 156,244 | 6.83 |
| 2026-01-30 | 1,135,240 | +4.0% | 422,528 | 2.69 |
| 2026-01-15 | 1,091,135 | -1.4% | 178,569 | 6.11 |
| 2025-12-31 | 1,106,700 | -7.7% | 184,074 | 6.01 |
| 2025-12-15 | 1,198,701 | -3.4% | 468,079 | 2.56 |
| 2025-11-28 | 1,240,508 | -13.9% | 584,274 | 2.12 |
| 2025-11-14 | 1,441,185 | +24.1% | 1,452,423 | 1.00 |
| 2025-10-31 | 1,161,662 | +9.1% | 197,567 | 5.88 |
| 2025-10-15 | 1,064,456 | -22.3% | 282,849 | 3.76 |
| 2025-09-30 | 1,369,925 | -7.3% | 237,719 | 5.76 |
| 2025-09-15 | 1,478,457 | +22.7% | 348,066 | 4.25 |
| 2025-08-29 | 1,204,826 | -2.9% | 125,996 | 9.56 |
Daily short volume
FINRA Reg SHO, last 60 sessions. JSONAs of 11 September 2026, the short share of KRRO volume is 55.5%, down 22.7 points over the last five sessions. Over the last 52 readings it ranged from 38.5% (8 September 2026) to 85.3% (23 July 2026). The latest reading is 8.1 points below the 30-session average of 63.6%, on 81K shares reported.
| Date | Short volume | Total volume | Short share | Exempt |
|---|---|---|---|---|
| 2026-09-11 | 45K | 81K | 55.5% | 8,500 |
| 2026-09-10 | 46K | 56K | 82.2% | 0 |
| 2026-09-09 | 36K | 50K | 71.1% | 0 |
| 2026-09-08 | 17K | 45K | 38.5% | 0 |
| 2026-09-04 | 13K | 27K | 48.7% | 0 |
| 2026-09-03 | 28K | 35K | 78.2% | 0 |
| 2026-09-02 | 21K | 26K | 78.1% | 0 |
| 2026-09-01 | 15K | 19K | 81.5% | 0 |
| 2026-08-31 | 17K | 21K | 80.4% | 0 |
| 2026-08-28 | 14K | 21K | 66.4% | 0 |
| 2026-08-27 | 11K | 14K | 75.5% | 0 |
| 2026-08-26 | 9K | 15K | 61.2% | 219 |
| 2026-08-25 | 17K | 28K | 59.9% | 0 |
| 2026-08-24 | 15K | 23K | 65.2% | 0 |
| 2026-08-21 | 7K | 15K | 46.4% | 0 |
| 2026-08-20 | 14K | 20K | 69.8% | 7 |
| 2026-08-19 | 26K | 45K | 59.2% | 6,600 |
| 2026-08-18 | 14K | 25K | 54.4% | 0 |
| 2026-08-17 | 13K | 32K | 42.5% | 0 |
| 2026-08-14 | 11K | 17K | 65.5% | 0 |
| 2026-08-13 | 30K | 45K | 65.5% | 0 |
| 2026-08-12 | 25K | 36K | 71.2% | 0 |
| 2026-08-11 | 21K | 36K | 57.2% | 300 |
| 2026-08-10 | 11K | 29K | 38.7% | 0 |
| 2026-08-07 | 18K | 31K | 57.5% | 0 |
| 2026-08-06 | 19K | 25K | 75.6% | 0 |
| 2026-08-05 | 30K | 42K | 71.6% | 0 |
| 2026-08-04 | 20K | 45K | 44.0% | 24 |
| 2026-08-03 | 29K | 40K | 73.7% | 0 |
| 2026-07-31 | 33K | 44K | 74.0% | 0 |
Fails to deliver
SEC, by settlement date. JSONAs of 14 August 2026, the fails-to-deliver balance in KRRO is 3 shares, down 6,024 shares over the last settlement date. Over the last 52 readings it ranged from 2 shares (19 February 2026) to 492,744 shares (28 January 2026). The latest reading sits at the bottom of that range.
| Settlement | Shares failed | Price | Value |
|---|---|---|---|
| 2026-08-14 | 3 | $13.29 | $40 |
| 2026-08-10 | 6,027 | $13.25 | $80K |
| 2026-08-05 | 118 | $11.35 | $1K |
| 2026-08-03 | 4,695 | $10.37 | $49K |
| 2026-07-31 | 3,190 | $10.45 | $33K |
| 2026-07-30 | 4,681 | $10.07 | $47K |
| 2026-07-28 | 15,172 | $10.72 | $163K |
| 2026-07-24 | 55 | $11.53 | $634 |
| 2026-07-22 | 18,769 | $11.96 | $224K |
| 2026-07-17 | 8,182 | $12.28 | $100K |
| 2026-07-16 | 7,624 | $13.03 | $99K |
| 2026-07-15 | 1,525 | $13.27 | $20K |
| 2026-07-13 | 18,314 | $14.56 | $267K |
| 2026-07-08 | 40,345 | $14.49 | $585K |
| 2026-07-07 | 758 | $14.06 | $11K |
| 2026-07-02 | 1,666 | $13.65 | $23K |
| 2026-06-24 | 1,382 | $13.71 | $19K |
| 2026-06-22 | 200 | $12.99 | $3K |
| 2026-06-15 | 5,643 | $11.61 | $66K |
| 2026-06-12 | 51 | $10.53 | $537 |
| 2026-06-11 | 6 | $10.59 | $64 |
| 2026-06-04 | 6 | $11.08 | $66 |
| 2026-04-29 | 12 | $12.80 | $154 |
| 2026-04-28 | 6 | $12.84 | $77 |
| 2026-04-24 | 1,825 | $13.60 | $25K |
| 2026-04-20 | 12 | $14.39 | $173 |
| 2026-04-17 | 7,671 | $13.47 | $103K |
| 2026-04-16 | 32 | $13.68 | $438 |
| 2026-04-15 | 643 | $13.93 | $9K |
| 2026-04-14 | 6 | $13.69 | $82 |
Insider trades
SEC Form 4, newest first. JSONOver the last 90 days KRRO insiders reported 2 open-market buys ($79K) against 5 sells ($491K), so the dollar flow leans toward selling. Latest filing: FORMELA JEAN FRANCOIS on 2026-08-19.
| Date | Insider | Title | Type | Shares | Price | Value | Owned after |
|---|---|---|---|---|---|---|---|
| 2026-08-19 | FORMELA JEAN FRANCOIS | n/a | Sell | 5K | $14.00 | $68K | 141K |
| 2026-08-19 | FORMELA JEAN FRANCOIS | n/a | Sell | 24K | $14.00 | $330K | 681K |
| 2026-08-11 | FORMELA JEAN FRANCOIS | n/a | Sell | 368 | $13.96 | $5K | 146K |
| 2026-08-11 | FORMELA JEAN FRANCOIS | n/a | Sell | 2K | $13.96 | $25K | 705K |
| 2026-08-10 | Lynx1 Capital Management LP | n/a | Buy | 1K | $13.19 | $19K | 1.5M |
| 2026-08-06 | Lynx1 Capital Management LP | n/a | Buy | 5K | $11.40 | $60K | 1.5M |
| 2026-08-04 | Aiyar Ram | President and CEO | Sell | 6K | $10.84 | $63K | 69K |
| 2026-05-29 | Aiyar Ram | President and CEO | Sell | 15K | $12.98 | $197K | 75K |
| 2026-05-28 | FORMELA JEAN FRANCOIS | n/a | Sell | 419 | $13.95 | $6K | 195K |
| 2026-05-28 | FORMELA JEAN FRANCOIS | n/a | Sell | 2K | $13.95 | $34K | 940K |
| 2026-05-26 | Aiyar Ram | President and CEO | Grant | 50K | $12.33 | $617K | 90K |
| 2026-03-31 | Lynx1 Capital Management LP | n/a | Buy | 520 | $10.60 | $6K | 1.5M |
| 2026-03-10 | Yang Rick | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | SANDELL SCOTT D | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | New Enterprise Associates 17, L.P. | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | Mathers Edward T | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | Walker Paul Edward | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | Makhzoumi Mohamad | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | Florence Anthony A. Jr. | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | Chang Carmen | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | Behbahani Ali | n/a | Grant | 207K | $11.11 | $2.3M | 1.3M |
| 2026-03-10 | BASKETT FOREST | n/a | Buy | 207K | $11.11 | $2.3M | 1.3M |
| 2026-02-02 | Aiyar Ram | President and CEO | Grant | 40K | $0.00 | $0 | 40K |
| 2025-12-15 | Vincent Loic A | Chief Scientific Officer | Grant | 22K | $0.00 | $0 | 22K |
| 2025-12-15 | Dolan Oliver | Senior Vice President, Finance | Grant | 21K | $0.00 | $0 | 21K |
| 2025-12-15 | Chappell Todd | Chief Operating Officer | Grant | 20K | $0.00 | $0 | 20K |
| 2025-12-15 | Cerio Jeffrey | General Counsel | Grant | 42K | $0.00 | $0 | 42K |
Form 4 filings are due within two business days of the trade. Insiders sell for many reasons that say nothing about the company; open-market buys are the rarer, stronger signal.
Planned sales (Form 144)
Newest first. JSON4 Form 144 notices on file for KRRO worth $762K at the prices reported; 4 in the last 90 days worth $762K. Latest: Dolan Oliver filed on 2026-09-11 to sell 5 shares ($69) from 2026-09-11.
| Filed | Seller | Shares | Market value | Of outstanding | Sale from | Broker |
|---|---|---|---|---|---|---|
| 2026-09-11 | Dolan OliverOfficer | 5 | $69 | 0.000% | 2026-09-11 | Fidelity Brokerage Services LLC |
| 2026-09-09 | Dolan OliverOfficer | 6 | $82 | 0.000% | 2026-09-09 | Fidelity Brokerage Services LLC |
| 2026-09-08 | Dolan OliverOfficer | 7K | $99K | 0.050% | 2026-09-08 | Fidelity Brokerage Services LLC |
| 2026-08-04 | Aiyar RamOfficer, Director | 6K | $663K | 0.040% | 2026-08-04 | Fidelity Brokerage Services LLC |
Large holders (13D and 13G)
One row per reporting person, newest filing first. JSON6 holders above 5% have filed on KRRO, 6 on Schedule 13D (active intent). The largest reported stake is Atlas Venture Fund XI, L.P. at 4.9% of the class (706,556 shares), filed 2026-08-04 for an event on 2026-06-24.
| Filed | Form | Holder | Shares | Of class | Event |
|---|---|---|---|---|---|
| 2026-08-04 | 13D/Ano. 1 | Atlas Venture Fund XI, L.P.partnership | 707K | 4.9% | 2026-06-24 |
| 2026-08-04 | 13D/Ano. 1 | Atlas Venture Associates XI, L.P.partnership | 707K | 4.9% | 2026-06-24 |
| 2026-08-04 | 13D/Ano. 1 | Atlas Venture Associates XI, LLCother entity | 707K | 4.9% | 2026-06-24 |
| 2026-08-04 | 13D/Ano. 1 | Atlas Venture Opportunity Fund II, L.P.partnership | 146K | 1.0% | 2026-06-24 |
| 2026-08-04 | 13D/Ano. 1 | Atlas Venture Associates Opportunity II, L.P.partnership | 146K | 1.0% | 2026-06-24 |
| 2026-08-04 | 13D/Ano. 1 | Atlas Venture Associates Opportunity II, LLCother entity | 146K | 1.0% | 2026-06-24 |
13F holders
Tracked managers holding KRRO at their latest 13F. JSON6 of the 30 tracked managers held KRRO at their latest 13F, $11.4M in total at quarter-end prices. AQR Capital Management is the largest at $3.9M (0.0% of its portfolio) as of 2026-06-30. Over the prior quarter 4 added shares and 2 cut.
| Fund | Quarter | Shares | Value | Of portfolio | Change in shares |
|---|---|---|---|---|---|
| AQR Capital Management | 2026-06-30 | 299K | $3.9M | 0.00% | +31K |
| Two Sigma Investments | 2026-06-30 | 178K | $2.3M | 0.00% | +13K |
| Citadel Advisors | 2026-06-30 | 124K | $1.6M | 0.00% | -145K |
| Millennium Management | 2026-06-30 | 118K | $1.6M | 0.00% | +55K |
| Renaissance Technologies | 2026-06-30 | 111K | $1.5M | 0.00% | -26K |
| D. E. Shaw & Co. | 2026-06-30 | 34K | $451K | 0.00% | +10K |
Only the 30 tracked managers on the funds hub; a 13F reports long positions in US listed stock at quarter end, 45 days late, and says nothing about shorts or positions sold since.
What this page is
Korro Bio, Inc. in the regulatory record
Regulators publish company data in separate files that never sit next to each other: FINRA's twice-monthly short interest, its daily short sale volume, the SEC's fails-to-deliver counts, and each insider's Form 4. A company page pulls every series the site collects for one ticker onto one URL, keyed by the SEC's own ticker list, so the short position, the daily flow, the settlement fails and what insiders are doing can be read together.
Each section has its own history table, a summary sentence built from the rows (last value, change, range with dates) and its own JSON and CSV links. Nothing on the page is written by a model; the sentences change only when the data does. A page exists only for companies with data in at least two series, and every section says when its source last updated.
This page follows Korro Bio, Inc. (KRRO), SEC CIK 1703647, listed on Nasdaq. The cross-market tables live on the short interest and insider transactions hubs.
Source and method
- Short interest
- FINRA consolidated short interestTwice a month, about eight business days after settlement. Latest 2026-08-14.JSON and CSV
- Daily short volume
- FINRA Reg SHO daily filesEvery trading day, loaded the following morning. Latest 2026-09-11.JSON and CSV
- Fails to deliver
- SEC fails-to-deliver dataTwice a month, a few weeks after the half month ends. Latest 2026-08-14.JSON and CSV
- Planned sales
- SEC EDGAR Form 144EDGAR read every 30 minutes; a notice is filed on or before the sell order. Latest 2026-09-11.JSON and CSV
- Large holders
- SEC EDGAR Schedule 13D and 13GEDGAR read every 30 minutes; 13D within five business days of crossing 5%, 13G on the passive schedule. Latest 2026-08-04.JSON and CSV
- 13F holders
- SEC EDGAR Form 13F-HRQuarterly, filed within 45 days of quarter end; 30 tracked managers. Latest 2026-06-30.JSON and CSV
- Insider trades
- SEC EDGAR Form 4EDGAR read every 30 minutes; filings are due two business days after the trade. Latest 2026-08-19.JSON and CSV
- Company record
- EDGAR filing index for CIK 1703647Ticker, name and exchange from the SEC's company list, refreshed weekly.
- Rate limits
- 30 requests a minute without a key, 120 a minute with a key from a free account.
Data checks. Every dataset is checked against its source once a day. This dataset passed the last run, 12 Sep 05:40 UTC.
How to read it
- Read the position against the flow: rising short interest with a high daily short share is new shorting; rising short interest with a normal short share is old shorts holding on.
- Insider buys next to a crowded short are the combination that has historically preceded squeezes; insider sells next to a crowded short are common and mean little.
- Fails to deliver matter relative to the float, not in absolute shares; a million failed shares in a mega cap is noise.
Analysis of what the data shows, not advice. XOOMAR does not recommend buying, selling or holding anything.
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Datasets
Frequently Asked Questions
How much of KRRO is sold short?
What is KRRO's daily short volume?
Does KRRO have fails to deliver?
Are KRRO insiders buying or selling?
Have KRRO insiders filed to sell?
Who owns more than 5% of KRRO?
Which funds hold KRRO?
Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.