Amprius Technologies, Inc. (AMPX)

Every FINRA and SEC series the site collects for Amprius Technologies, Inc.: short interest with days to cover, daily short sale volume, fails to deliver and Form 4 insider trades. Listed on NYSE, classified by the SEC as miscellaneous electrical machinery, equipment & supplies.

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22.1M

Short interest

settlement 2026-08-14

3.1

Days to cover

-7.4% vs prior

39.5%

Short share of volume

2026-09-11

1,927

Fails to deliver

settlement 2026-08-11

-$2.7M

Insider flow, 90 days

0 buys, 5 sells

As of 2026-09-11.

Short interest

FINRA, twice a month; the last 12 months shown, all 48 settlements in the JSON

As of 14 August 2026, short interest in AMPX is 22,146,891 shares, down 5,887,718 shares over the last month. Over the last 48 readings it ranged from 2,468,709 shares (30 August 2024) to 28,034,609 shares (15 July 2026). At the reported average volume of 7.2M shares a day that is 3.1 days to cover.

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Settlement	Shares short	Change	Avg daily volume	Days to cover
2026-08-14	22,146,891	-7.4%	7,163,836	3.09
2026-07-31	23,928,102	-14.7%	5,752,370	4.16
2026-07-15	28,034,609	+6.6%	6,644,710	4.22
2026-06-30	26,309,329	+15.3%	8,191,705	3.21
2026-06-15	22,816,138	-11.0%	7,285,767	3.13
2026-05-29	25,637,309	+13.0%	10,894,061	2.35
2026-05-15	22,692,523	-2.3%	10,110,297	2.24
2026-04-30	23,225,858	+7.8%	8,535,425	2.72
2026-04-15	21,551,498	+20.3%	7,288,161	2.96
2026-03-31	17,909,138	+0.3%	7,882,322	2.27
2026-03-13	17,846,503	-6.8%	13,965,363	1.28
2026-02-27	19,141,715	+12.3%	5,976,839	3.20
2026-02-13	17,042,918	-3.3%	9,160,955	1.86
2026-01-30	17,620,761	+2.2%	9,869,914	1.79
2026-01-15	17,246,418	+5.9%	6,964,389	2.48
2025-12-31	16,283,031	+22.5%	5,914,386	2.75
2025-12-15	13,292,515	-1.6%	4,980,428	2.67
2025-11-28	13,514,161	-15.9%	5,902,338	2.29
2025-11-14	16,066,241	+4.6%	9,691,339	1.66
2025-10-31	15,356,669	-8.9%	8,332,213	1.84
2025-10-15	16,851,368	-6.5%	10,978,414	1.53
2025-09-30	18,024,182	+32.0%	10,513,255	1.71
2025-09-15	13,651,786	+19.1%	7,401,104	1.84
2025-08-29	11,457,481	+13.7%	5,052,274	2.27

Daily short volume

FINRA Reg SHO, last 60 sessions. JSON

As of 11 September 2026, the short share of AMPX volume is 39.5%, down 0.1 points over the last five sessions. Over the last 52 readings it ranged from 27.6% (2 September 2026) to 55.0% (13 July 2026). The latest reading is 2.6 points below the 30-session average of 42.1%, on 1.5M shares reported.

Date	Short volume	Total volume	Short share	Exempt
2026-09-11	583K	1.5M	39.5%	10,968
2026-09-10	545K	1.4M	37.7%	2,416
2026-09-09	1.2M	2.4M	48.9%	8,385
2026-09-08	1.2M	2.4M	49.1%	1,279
2026-09-04	904K	1.9M	46.8%	7,091
2026-09-03	621K	1.6M	39.6%	15,980
2026-09-02	583K	2.1M	27.6%	111
2026-09-01	543K	1.4M	38.5%	5,428
2026-08-31	604K	1.3M	45.5%	9,497
2026-08-28	602K	1.5M	39.5%	6,250
2026-08-27	659K	1.2M	54.1%	696
2026-08-26	904K	1.9M	46.7%	5,167
2026-08-25	702K	1.5M	46.2%	500
2026-08-24	653K	1.5M	42.5%	8,000
2026-08-21	483K	1.5M	32.3%	1,700
2026-08-20	828K	2.1M	40.1%	1,100
2026-08-19	757K	1.9M	39.3%	2,185
2026-08-18	813K	2.2M	37.6%	7,698
2026-08-17	1.2M	3.1M	37.8%	6,030
2026-08-14	1.5M	3.6M	41.8%	2,665
2026-08-13	651K	1.6M	41.0%	0
2026-08-12	747K	1.7M	43.2%	735
2026-08-11	826K	1.6M	50.6%	2,834
2026-08-10	1.3M	2.8M	47.4%	5
2026-08-07	697K	2.2M	31.5%	5
2026-08-06	1.6M	3.2M	49.0%	983
2026-08-05	1.8M	4.6M	39.6%	8,460
2026-08-04	1.4M	3.0M	45.1%	11,026
2026-08-03	797K	1.9M	41.8%	2,300
2026-07-31	822K	1.9M	43.0%	0

Fails to deliver

SEC, by settlement date. JSON

As of 11 August 2026, the fails-to-deliver balance in AMPX is 1,927 shares, up 1,747 shares over the last settlement date. Over the last 52 readings it ranged from 11 shares (26 March 2026) to 1,179,933 shares (2 April 2026). The latest reading sits at the bottom of that range.

Settlement	Shares failed	Price	Value
2026-08-11	1,927	$11.81	$23K
2026-08-05	180	$10.81	$2K
2026-07-27	30,885	$9.24	$285K
2026-07-24	1,521	$9.91	$15K
2026-07-17	591	$10.10	$6K
2026-06-30	2,370	$13.52	$32K
2026-06-26	22	$12.56	$276
2026-06-18	61	$15.00	$915
2026-06-15	2,172	$16.31	$35K
2026-06-08	5,971	$19.69	$118K
2026-06-05	1,135	$22.54	$26K
2026-06-03	106	$22.91	$2K
2026-06-02	1,478	$21.75	$32K
2026-06-01	1,411	$20.28	$29K
2026-04-28	75	$21.42	$2K
2026-04-24	25,316	$21.73	$550K
2026-04-22	1,684	$21.43	$36K
2026-04-21	3,544	$19.61	$69K
2026-04-20	207,645	$18.67	$3.9M
2026-04-17	188,067	$19.13	$3.6M
2026-04-15	1,905	$17.89	$34K
2026-04-14	703	$18.39	$13K
2026-04-13	15,925	$17.22	$274K
2026-04-09	752	$16.92	$13K
2026-04-06	18	$16.00	$288
2026-04-02	1,179,933	$15.52	$18.3M
2026-03-27	2,820	$17.16	$48K
2026-03-26	11	$17.93	$197
2026-03-23	1,600	$18.20	$29K
2026-03-20	6,539	$19.11	$125K

Insider trades

SEC Form 4, newest first, 50 of 86 shown. JSON

Insiders at AMPX reported 5 open-market sells worth $2.7M in the last 90 days and no open-market buys. Sells alone are a weak signal; insiders sell for tax, diversification and estate reasons all the time. Latest filing: Stepien Thomas M (Chief Executive Officer) on 2026-08-25.

Date	Insider	Title	Type	Shares	Price	Value	Owned after
2026-08-25	Stepien Thomas M	Chief Executive Officer	Grant	346	$0.00	$0	37K
2026-08-25	Stepien Thomas M	Chief Executive Officer	Gift	346	$0.00	$0	579K
2026-08-25	Stepien Thomas M	Chief Executive Officer	Gift	5K	$0.00	$0	589K
2026-08-24	Stepien Thomas M	Chief Executive Officer	Sell	8K	$10.03	$80K	594K
2026-08-21	Stepien Thomas M	Chief Executive Officer	Sell	24K	$10.34	$243K	602K
2026-08-21	Stefan Constantin Ionel	Chief Technology Officer	Sell	30K	$10.34	$307K	772K
2026-08-21	Sun Kang	n/a	Sell	62K	$10.34	$642K	1.2M
2026-06-15	DIXON DONALD R	n/a	Sell	85K	$17.17	$1.5M	359K
2026-06-12	SATTERTHWAITE LIVINGSTON	n/a	Grant	10K	$0.00	$0	347K
2026-06-12	Chu Steven	n/a	Grant	10K	$0.00	$0	138K
2026-06-12	BAYLESS KATHLEEN A	n/a	Grant	10K	$0.00	$0	216K
2026-06-12	DIXON DONALD R	n/a	Grant	10K	$0.00	$0	280K
2026-06-09	DIXON DONALD R	n/a	Sell	40K	$19.13	$765K	444K
2026-06-04	Stepien Thomas M	Chief Executive Officer	Sell	2K	$20.97	$42K	626K
2026-06-04	Stepien Thomas M	Chief Executive Officer	Gift	37K	$0.00	$0	628K
2026-06-04	Stepien Thomas M	Chief Executive Officer	Gift	30K	$0.00	$0	665K
2026-05-27	Stepien Thomas M	Chief Executive Officer	Sell	4K	$17.19	$75K	695K
2026-05-27	Stefan Constantin Ionel	Chief Technology Officer	Sell	3K	$17.19	$55K	801K
2026-05-27	Sun Kang	n/a	Sell	356	$17.19	$6K	1.3M
2026-05-26	DIXON DONALD R	n/a	Sell	18K	$17.90	$320K	484K
2026-05-21	Stepien Thomas M	Chief Executive Officer	Sell	61K	$14.79	$898K	699K
2026-05-21	Stefan Constantin Ionel	Chief Technology Officer	Sell	29K	$14.79	$426K	805K
2026-05-21	Sun Kang	n/a	Sell	68K	$14.79	$1.0M	1.3M
2026-05-05	Sun Kang	n/a	Grant	6K	$0.00	$0	1.3M
2026-04-01	Sun Kang	n/a	Sell	249K	$16.78	$4.2M	1.3M
2026-04-01	Sun Kang	n/a	Sell	1.3M	$15.73	$19.7M	1.6M
2026-04-01	Sun Kang	n/a	Option exercise	187K	$3.68	$690K	2.8M
2026-04-01	Sun Kang	n/a	Option exercise	1.3M	$1.78	$2.3M	2.7M
2026-03-23	Sun Kang	n/a	Sell	65K	$19.06	$1.2M	56K
2026-03-23	Sun Kang	n/a	Sell	153K	$18.69	$2.9M	121K
2026-03-12	Chu Steven	n/a	Sell	6K	$18.53	$103K	127K
2026-03-12	Chu Steven	n/a	Sell	50K	$18.21	$911K	133K
2026-03-12	Chu Steven	n/a	Sell	100K	$18.65	$1.9M	183K
2026-03-12	Chu Steven	n/a	Option exercise	69K	$0.62	$43K	283K
2026-03-12	Chu Steven	n/a	Option exercise	86K	$2.61	$225K	213K
2026-03-12	HSIEH Wen Hsuan	n/a	Sell	131K	$18.22	$2.4M	44K
2026-03-12	HSIEH Wen Hsuan	n/a	Sell	283K	$18.55	$5.2M	175K
2026-03-12	HSIEH Wen Hsuan	n/a	Option exercise	270K	$2.61	$705K	458K
2026-03-10	Chu Steven	n/a	Sell	167K	$17.92	$3.0M	127K
2026-03-10	Chu Steven	n/a	Option exercise	104K	$0.62	$65K	294K
2026-03-04	Stepien Thomas M	Chief Executive Officer	Grant	150K	$0.00	$0	760K
2026-03-04	Stefan Constantin Ionel	Chief Technology Officer	Grant	110K	$0.00	$0	833K
2026-03-04	RODRIGUEZ RICARDO C.	Chief Financial Officer	Grant	150K	$0.00	$0	350K
2026-02-23	Stefan Constantin Ionel	Chief Technology Officer	Sell	25K	$10.16	$258K	723K
2026-02-23	Sun Kang	n/a	Sell	61K	$10.16	$622K	1.3M
2026-01-28	Stefan Constantin Ionel	Chief Technology Officer	Sell	40K	$12.00	$476K	749K
2026-01-28	Stefan Constantin Ionel	Chief Technology Officer	Option exercise	40K	$0.05	$2K	788K
2026-01-28	Stefan Constantin Ionel	Chief Technology Officer	Option exercise	90	$0.62	$56	749K
2026-01-23	Stefan Constantin Ionel	Chief Technology Officer	Sell	2K	$12.00	$19K	749K
2026-01-23	Stefan Constantin Ionel	Chief Technology Officer	Option exercise	2K	$0.05	$80	750K

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. JSON

1 Form 144 notice on file for AMPX worth $80K at the prices reported; 1 in the last 90 days worth $80K. Latest: THOMAS M STEPIEN filed on 2026-08-24 to sell 8,000 shares ($80K) from 2026-08-24.

Filed	Seller	Shares	Market value	Of outstanding	Sale from	Broker
2026-08-24	THOMAS M STEPIENOfficer, Director	8K	$80K	0.005%	2026-08-24	Morgan Stanley Smith Barney LLC Executive Financial Services

Large holders (13D and 13G)

One row per reporting person, newest filing first. JSON

4 holders above 5% have filed on AMPX, all on Schedule 13G (passive). The largest reported stake is BlackRock, Inc. at 7.4% of the class (10,700,817 shares), filed 2026-07-27 for an event on 2026-06-30.

Filed	Form	Holder	Shares	Of class	Event
2026-08-10	13G/Ano. 1	JANE STREET GROUP, LLCparent holding company	4.7M	3.3%	2026-06-30
2026-08-10	13G/Ano. 1	Jane Street Capital, LLCbroker-dealer	3.8M	2.7%	2026-06-30
2026-08-10	13G/Ano. 1	Jane Street Global Trading, LLCother entity	962K	0.7%	2026-06-30
2026-07-27	13G/Ano. 1	BlackRock, Inc.parent holding company	10.7M	7.4%	2026-06-30

13F holders

Tracked managers holding AMPX at their latest 13F. JSON

7 of the 30 tracked managers held AMPX at their latest 13F, $256.9M in total at quarter-end prices. Citadel Advisors is the largest at $73.0M (0.0% of its portfolio) as of 2026-06-30. Over the prior quarter 7 added shares and 0 cut.

Fund	Quarter	Shares	Value	Of portfolio	Change in shares
Citadel Advisors	2026-06-30	5.3M	$73.0M	0.01%	+1.1M
Point72 Asset Management	2026-06-30	4.4M	$60.7M	0.07%	+2.9M
Two Sigma Investments	2026-06-30	4.3M	$59.9M	0.04%	+813K
D. E. Shaw & Co.	2026-06-30	1.5M	$21.3M	0.01%	+411K
Millennium Management	2026-06-30	1.4M	$20.1M	0.01%	+1.4M
Renaissance Technologies	2026-06-30	1.4M	$19.5M	0.03%	+1.0M
AQR Capital Management	2026-06-30	173K	$2.4M	0.00%	+35K

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

Amprius Technologies, 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 Amprius Technologies, Inc. (AMPX), SEC CIK 1899287, listed on NYSE, classified by the SEC as miscellaneous electrical machinery, equipment & supplies. 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 2026-08-11.JSON and CSV
Planned sales: SEC EDGAR Form 144EDGAR read every 30 minutes; a notice is filed on or before the sell order. Latest 2026-08-24.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 2026-08-10.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 2026-08-25.JSON and CSV
Company record: EDGAR filing index for CIK 1899287Ticker, 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, 13 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.

Datasets

Frequently Asked Questions

How much of AMPX is sold short?

22,146,891 shares were held short at the 2026-08-14 settlement, 3.1 days of average volume. FINRA publishes the next count about eight business days after the 15th and the last business day of the month.

What is AMPX's daily short volume?

On 2026-09-11, 583,479 of the 1,478,429 AMPX shares reported to FINRA were sold short, 39.5% of the day's reported volume. Short volume is a flow for one day, not a position.

Does AMPX have fails to deliver?

The SEC's latest file shows 1,927 AMPX shares failed to deliver at settlement 2026-08-11. Fails are reported per settlement date and published twice a month with a lag.

Are AMPX insiders buying or selling?

Have AMPX insiders filed to sell?

1 Form 144 notice on file for AMPX worth $80K at the prices reported; 1 in the last 90 days worth $80K. Latest: THOMAS M STEPIEN filed on 2026-08-24 to sell 8,000 shares ($80K) from 2026-08-24.

Who owns more than 5% of AMPX?

Which funds hold AMPX?

Data on this page is provided for informational purposes only and is not financial advice. See our editorial policy.

Amprius Technologies, Inc. (AMPX)

Short interest

Daily short volume

Fails to deliver

Insider trades

Planned sales (Form 144)

Large holders (13D and 13G)

13F holders

Amprius Technologies, Inc. in the regulatory record

Source and method

How to read it

Other companies the SEC classifies as miscellaneous electrical machinery, equipment & supplies

Datasets

Frequently Asked Questions