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Rallybio Corp

RLYB
Exchange
Nasdaq
Industry
Pharmaceutical Preparations
SEC CIK
0001739410

In the last 90 days, Rallybio Corp insiders filed 0 open-market purchases and 1 sale; 37 institutions reported holding it in 13F filings for Q2 2026, worth $65.0M in total; Viking Global Investors is the only superinvestor holding it.

Four kinds of short-selling data, each measuring something different:

  • Short interest: shares sold short and not yet bought back, as of a settlement date. FINRA publishes it twice a month, about eight business days after the settlement date.
  • Daily short volume: shares sold short each day in off-exchange trades reported to FINRA. It counts trades, not open positions, and is published the next day.
  • Fails-to-deliver: shares not delivered by the settlement date. The SEC publishes them twice a month, about two weeks late.
  • ATS (dark pool) volume: weekly volume on alternative trading systems and other off-exchange venues. FINRA publishes it two to four weeks after the week.

More in the glossary.

Short interest

Shares sold short and not yet bought back, from FINRA, on every settlement date in the last two years.

Short interest
39.0K
Shares, settlement Oct 30, 2026
Change
−1.94K
−4.7% vs. Oct 15, 2026
Days to cover
1.18
Short interest ÷ average daily volume
Average daily volume
33.2K
Shares, as reported by FINRA
Short interest by settlement date
Oct 31, 2024: 463,356 sharesNov 15, 2024: 367,036 sharesNov 29, 2024: 354,056 sharesDec 13, 2024: 337,653 sharesDec 31, 2024: 353,969 sharesJan 15, 2025: 353,893 sharesJan 31, 2025: 350,193 sharesFeb 14, 2025: 331,091 sharesFeb 28, 2025: 337,529 sharesMar 14, 2025: 337,792 sharesMar 31, 2025: 345,912 sharesApr 15, 2025: 351,626 sharesApr 30, 2025: 363,424 sharesMay 15, 2025: 356,942 sharesMay 30, 2025: 318,870 sharesJun 13, 2025: 330,040 sharesJun 30, 2025: 346,362 sharesJul 15, 2025: 1,975,093 sharesJul 31, 2025: 1,346,454 sharesAug 15, 2025: 771,851 sharesAug 29, 2025: 612,420 sharesSep 15, 2025: 422,184 sharesSep 30, 2025: 331,509 sharesOct 15, 2025: 284,270 sharesOct 31, 2025: 229,838 sharesNov 14, 2025: 174,572 sharesNov 28, 2025: 140,389 sharesDec 15, 2025: 122,587 sharesDec 31, 2025: 106,204 sharesJan 15, 2026: 116,605 sharesJan 30, 2026: 141,643 sharesFeb 13, 2026: 38,974 sharesFeb 27, 2026: 44,517 sharesMar 13, 2026: 797,895 sharesMar 31, 2026: 1,108,870 sharesApr 15, 2026: 1,405,893 sharesApr 30, 2026: 1,572,902 sharesMay 15, 2026: 578,792 sharesMay 29, 2026: 586,906 sharesJun 15, 2026: 425,033 sharesJun 30, 2026: 408,746 sharesJul 15, 2026: 170,156 sharesJul 31, 2026: 63,485 sharesAug 14, 2026: 54,564 sharesAug 31, 2026: 54,943 sharesSep 15, 2026: 55,556 sharesSep 30, 2026: 49,245 sharesOct 15, 2026: 40,962 sharesOct 30, 2026: 39,026 shares
Short interest in RLYB by settlement date
Settlement dateShort interestChangeChange %Avg. daily volumeDays to cover
Oct 30, 202639.0K−1.94K−4.7%33.2K1.18
Oct 15, 202641.0K−8.28K−16.8%5.54K7.39
Sep 30, 202649.2K−6.31K−11.4%10.1K4.88
Sep 15, 202655.6K+613+1.1%11.0K5.04
Aug 31, 202654.9K+379+0.7%10.0K5.50
Aug 14, 202654.6K−8.92K−14.1%27.0K2.02
Jul 31, 202663.5K−106.7K−62.7%30.8K2.06
Jul 15, 2026170.2K−238.6K−58.4%48.1K3.54
Jun 30, 2026408.7K−16.3K−3.8%47.6K8.59
Jun 15, 2026425.0K−161.9K−27.6%86.5K4.92
May 29, 2026586.9K+8.11K+1.4%49.0K11.98
May 15, 2026578.8K−994.1K−63.2%1.00M1.00
Apr 30, 20261.57M+167.0K+11.9%54.5K28.85
Apr 15, 20261.41M+297.0K+26.8%68.0K20.66
Mar 31, 20261.11M+311.0K+39.0%108.4K10.23
Mar 13, 2026797.9K+753.4K+1,692.3%499.7K1.60
Feb 27, 202644.5K+5.54K+14.2%89.6K1.00
Feb 13, 2026Split39.0K−102.7K−72.5%25.0K1.56
Jan 30, 2026141.6K+25.0K+21.5%169.2K1.00
Jan 15, 2026116.6K+10.4K+9.8%118.8K1.00
Dec 31, 2025106.2K−16.4K−13.4%223.1K1.00
Dec 15, 2025122.6K−17.8K−12.7%153.4K1.00
Nov 28, 2025140.4K−34.2K−19.6%201.5K1.00
Nov 14, 2025174.6K−55.3K−24.1%210.6K1.00
Oct 31, 2025229.8K−54.4K−19.2%286.8K1.00
Oct 15, 2025284.3K−47.2K−14.3%329.3K1.00
Sep 30, 2025331.5K−90.7K−21.5%320.2K1.04
Sep 15, 2025422.2K−190.2K−31.1%367.3K1.15
Aug 29, 2025612.4K−159.4K−20.7%307.8K1.99
Aug 15, 2025771.9K−574.6K−42.7%552.8K1.40
Jul 31, 20251.35M−628.6K−31.8%557.5K2.42
Jul 15, 20251.98M+1.63M+470.2%16.1M1.00
Jun 30, 2025346.4K+16.3K+5.0%184.1K1.88
Jun 13, 2025330.0K+11.2K+3.5%463.0K1.00
May 30, 2025318.9K−38.1K−10.7%92.1K3.46
May 15, 2025356.9K−6.48K−1.8%72.2K4.94
Apr 30, 2025363.4K+11.8K+3.4%89.1K4.08
Apr 15, 2025351.6K+5.71K+1.7%295.6K1.19
Mar 31, 2025345.9K+8.12K+2.4%46.4K7.46
Mar 14, 2025337.8K+263+0.1%42.0K8.04
Feb 28, 2025337.5K+6.44K+1.9%60.1K5.61
Feb 14, 2025331.1K−19.1K−5.5%85.6K3.87
Jan 31, 2025350.2K−3.70K−1.1%44.6K7.85
Jan 15, 2025353.9K−760.0%66.0K5.36
Dec 31, 2024354.0K+16.3K+4.8%127.7K2.77
Dec 13, 2024337.7K−16.4K−4.6%110.3K3.06
Nov 29, 2024354.1K−13.0K−3.5%59.4K5.96
Nov 15, 2024367.0K−96.3K−20.8%71.0K5.17
Oct 31, 2024463.4K−73.3K−13.7%97.7K4.75

Fails-to-deliver

Shares that weren't delivered by the settlement date, from the SEC, for the last 30 dates with fails. The price is the previous day's closing price published by the SEC.

Fails-to-deliver in RLYB by settlement date
Settlement dateSharesPriceValue
Oct 9, 2026149$16.99$2.53K
Oct 8, 2026195$16.93$3.30K
Sep 21, 2026232$17.19$3.99K
Sep 17, 2026502$17.09$8.58K
Sep 4, 202612$16.88$202.56
Sep 2, 20261,213$16.69$20.2K
Aug 20, 202615$17.00$255
Aug 10, 202654$16.16$872.64
Aug 7, 202652$16.19$841.88
Aug 3, 20269$15.93$143.37
Jul 31, 202619$16.07$305.33
Jul 28, 202665$16.31$1.06K
Jul 27, 2026245$16.31$4.00K
Jul 17, 2026600$15.96$9.58K
Jun 26, 20266,744$15.71$105.9K
Jun 24, 202654$15.70$847.8
Jun 17, 202646$15.90$731.4
Jun 5, 20262,366$16.20$38.3K
May 29, 2026173$14.52$2.51K
May 28, 2026178$14.53$2.59K
May 27, 2026183$14.70$2.69K
May 26, 20265,112$15.88$81.2K
May 22, 2026367$15.38$5.64K
May 21, 2026601$14.58$8.76K
May 19, 20264,579$14.10$64.6K
May 18, 20263$14.30$42.9
May 15, 20265,737$14.21$81.5K
May 14, 20266,547$14.35$93.9K
May 13, 20261,595$14.03$22.4K
May 11, 20261,816$14.38$26.1K

Daily short volume

Off-exchange short-sale volume, not short interest: shares sold short each day in trades reported to FINRA, for the last 30 trading days.

The short volume ratio isn't a sentiment gauge: market makers sell short to fill buy orders and to hedge, so short sales are usually about half of off-exchange volume.

Off-exchange short volume in RLYB by trade date
Trade dateShort volumeShort exemptOff-exchange volumeShort volume ratio
Nov 10, 20263,41505,47262.4%
Nov 9, 2026930408,73110.7%
Nov 6, 20265,792014,06541.2%
Nov 5, 20261,9613224,85540.4%
Nov 4, 20266,130013,17546.5%
Nov 3, 20265,413015,82134.2%
Nov 2, 202616,53710,52434,36348.1%
Oct 30, 20262,663025,55810.4%
Oct 29, 202622,25115,82725,58587.0%
Oct 28, 20263,87508,05248.1%
Oct 27, 20267,7717,07311,75766.1%
Oct 26, 202612101,17410.3%
Oct 23, 202665402,44926.7%
Oct 22, 202677201,80542.8%
Oct 21, 202646405,4478.5%
Oct 20, 2026118048524.3%
Oct 19, 20261,23704,25429.1%
Oct 16, 20261,83603,82947.9%
Oct 15, 202654001,20145.0%
Oct 14, 202646901,69527.7%
Oct 13, 20265407617.1%
Oct 12, 202610001,9935.0%
Oct 9, 20261,55802,08174.9%
Oct 8, 202635901,21129.6%
Oct 7, 202689102,05143.4%
Oct 6, 202682026630.8%
Oct 5, 2026124065518.9%
Oct 2, 202653703,00917.8%
Oct 1, 202618503,0786.0%
Sep 30, 2026123060120.5%

ATS (dark pool) volume

Weekly volume on alternative trading systems (ATS) and other off-exchange (OTC) venues, from FINRA, for the last 12 weeks. ATS share is ATS volume ÷ (ATS + OTC volume), not a share of all trading.

Weekly ATS and OTC volume in RLYB
Week ofTierATS sharesATS tradesOther OTC sharesOther OTC tradesATS share
Oct 5, 2026T23,548832,83720255.6%
Sep 28, 2026T26,6726478,52625543.9%
Sep 21, 2026T24,2972962,52824263.0%
Sep 14, 2026T27,68231111,85028239.3%
Sep 7, 2026T24,8692762,89522162.7%
Aug 31, 2026T212,4824538,98736158.1%
Aug 24, 2026T25,6273513,73431560.1%
Aug 17, 2026T212,1267404,47033273.1%
Aug 10, 2026T229,06583911,06731772.4%
Aug 3, 2026T225,44993929,30742846.5%
Jul 27, 2026T217,9225747,26446671.2%
Jul 20, 2026T278,1261,74710,92661487.7%