🔔 Stock Alert Board

Set price-cross, % change and RSI conditions on the stocks you follow; while the page is open you get a sound and browser notification when one is met. US stocks plus Korean names like Samsung Electronics and SK hynix. Prices may be delayed. Not investment advice.

Loading Data: Yahoo Finance (via our server, may be delayed)

Alerts only work while this page is open. Closing it stops them. Leaving it on a spare monitor or tablet with "Keep screen on" works well. Prices arrive 15–20 minutes late or more depending on the exchange, and rules are only checked on fresh quotes from a live session.

Add an alert rule

Alert log

Export / import settings

Price, day change, market status and quote time come from today's 5-minute bars, and RSI(14) and N-day highs/lows from one year of daily bars — both fetched from Yahoo Finance by our server and shared by all visitors through a cache. RSI and highs/lows use "daily bars up to the previous session + the current price"; the gap is the first 5-minute bar's open versus the previous close. Only stocks with rules are fetched, one at a time with spacing: about every minute while their market is open and about every 5 minutes when it is closed. Rules are checked only on a quote whose time is newer than the last one, while the market is open (or within 45 minutes of the close), so stale weekend or holiday prices never fire. A rule that is already true when you add it fires only after it turns false and then true again. Korean regular hours are 09:00–15:30 KST; US hours are 22:30–05:00 KST during US daylight time (23:30–06:00 otherwise). Pre-market and after-hours prices are not included.

Fetching pauses while the tab is hidden (turn on "Check while hidden" to keep going; enabling browser alerts turns it on too). On phones or in power-saving mode the browser may freeze the tab, and no alerts arrive meanwhile. Rules and the log stay only in this browser's localStorage (keys xc:stock_alert:cfg and xc:stock_alert:log) and are never sent to a server. Shortcuts: / = search, Esc = close.

For information only, not investment advice. Prices come from Yahoo Finance via our server and may be delayed 15–20 minutes or more depending on the exchange, or interrupted. Charts: TradingView Lightweight Charts™

What this tool does

A stock alert board: set conditions on the stocks you follow, and while this page is open it tells you the moment one is met — with a sound, a browser notification and a flashing tab title. Five rule types work for US stocks and Korean names such as Samsung Electronics and SK hynix: price rising above or falling below a level, % change versus the previous close, daily RSI(14) crossing a level, a new N-day high or low, and an opening gap of at least X% versus the previous close. Each rule fires once, every time (with a rest period), or once a day, and every alert is logged with its time and the quote time. Rules and the log stay on this device.

How it is calculated

Prices come from Yahoo Finance via our server, which serves a cache shared by all visitors (stock data sources cannot be called from the browser directly). For each stock, today's 5-minute bars (cached about a minute on the server) give the price, previous close, whether the market is open, the quote time and today's first open; one year of daily bars (cached 5 minutes) gives RSI and the high/low history. % change = price ÷ previous close − 1; gap = today's first 5-minute open ÷ previous close − 1. RSI(14) uses Wilder's method on daily closes up to the previous session plus the current price. A new N-day high means the price is above the highest high of the prior N sessions (today excluded), a new low means below the lowest low (52-week uses the whole year received). Each rule is armed while its condition is false and fires only when it turns true; it re-arms after price-type rules move back 0.2%, RSI moves back 2 points, or % change falls under half the threshold. A rule already true when added fires only after it turns false and true again. Rules are checked only on a quote newer than the last one, while the market is open (or within 45 minutes of the close), so stale weekend or holiday prices never fire — nor does the first quote after you open the page. Only stocks with active rules are refetched: about every minute while open and every 5 minutes when closed, one at a time, 0.5 s apart, pausing while the tab is hidden (unless "Check while hidden" is on). Rules and settings are stored in localStorage under xc:stock_alert:cfg and the log under xc:stock_alert:log.

Add stocks with the search box at the top (shortcut /) by name, ticker or 6-digit Korean code, or tap an example rule (e.g. Samsung Electronics down 5% vs previous close, NVDA RSI crossing below 30) to add the stock and the rule together

In "Add an alert rule", pick the stock, rule type, value and repeat mode, then press "Add rule". The "+ Alert rule" button on a card preselects that stock

Turn on sound and browser alerts. The browser asks for permission the first time; enabling browser alerts also turns on checking while hidden. Use "Test alert" to try the sound, notification and tab title

Each card shows the price, day change, open/closed status, quote time and delay, RSI(14) and the 20-day high/low, and each rule's state (armed, already true, fired, resting) with its current value

Leave the page open on a spare monitor or tablet with "Keep screen on" to use it as an alert panel. Move your rules to another device with "Export / import settings"

Reading the screen

Top bar: adding stocks, check status, alert options

The search box lists popular Korean, US and Japanese large caps and ETFs; for anything else type a ticker or 6-digit code and press Enter — the quote is fetched first (up to 20 stocks, 10 rules each). On the right you see the last check time and how many stocks have active rules. The buttons below are sound, browser alerts, check while hidden, keep screen on, and test alert.

Five rule types

Price cross: price rises to or above, or falls to or below a level. % change vs previous close: up or down by a percentage. RSI(14) daily: crosses above or below a level (1–99). New high/low: 5, 20, 60, 120 days or 52 weeks. Opening gap: today's first 5-minute open is at least X% above or below the previous close, once per session.

Repeat modes

"Fire once" turns the rule off after it fires; bring it back with "Turn on again" on the card. "Every time · 5 min / 15 min / 1 h rest" fires on every new crossing but skips crossings during the rest period. "Once a day" fires at most once per exchange date.

Stock cards

Price and day change, open/closed (regular session), daily RSI(14), today's gap, 20-day high/low, and the quote time with its delay. A green dot means armed; amber means already true or waiting to move back after firing. Stocks without rules are not refetched.

Alert log

The time, stock, rule, the value at the time and the quote time of the last 200 alerts. The tab title flashes "(count) 🔔 stock alert" when an alert fires, and keeps flashing until you return if the tab is hidden.

Things to know

Regular hours in Korea time: Korean stocks 09:00–15:30; US stocks 22:30–05:00 the next day during US daylight time (23:30–06:00 otherwise). Rules do not fire while a market is closed

Korean quotes arrive about 20 minutes late and US quotes can be delayed depending on the exchange. An alert means a delayed quote crossed your condition, not that the trade happened at that moment; the log records the quote time

"Every time · 15 min rest" fires on each new crossing but ignores crossings within 15 minutes of the last alert. Use a longer rest if the price keeps hovering around your level

Gap rules are judged once per session. If you add one after today's open, today's gap is skipped and the next session's open is checked

Phones often freeze the page when the screen turns off or you switch apps. For reliable alerts keep it open on a computer or a plugged-in tablet

Frequently asked questions

Do alerts arrive after I close the page?

No. Rules are never sent to a server; this page fetches quotes and checks them itself, so closing the page or having the browser freeze the tab stops the alerts. By default checking pauses while the tab is hidden; turn on "Check while hidden" to keep checking at the same pace.

How delayed are the prices?

Our server fetches from Yahoo Finance and caches for about a minute, and exchanges delay quotes by 15–20 minutes or more (Korean stocks about 20 minutes). Cards show the quote time and the delay, and the log records the quote time with each alert. It is not suited to fast trading alerts.

Why didn't my rule fire right after I added it?

A rule that is already true when added is shown as "Already true" and fires only after it turns false and then true again. The first quote after opening the page never fires either, so reloading doesn't repeat the same alert.

Can alerts fire on weekends or holidays?

No. When a market is closed the server marks it closed, and a quote whose time hasn't changed is not checked. Only the last trades that arrive within 45 minutes after the close (such as Korea's closing auction) are still considered.

Which bars does RSI use?

Daily RSI(14). It joins the current price to daily closes up to the previous session as if it were today's close, so it moves during the session and settles on the closing value afterwards. It may differ from a broker's app by a small fraction.

Where are rules stored, and can I move them?

Only in this browser's localStorage (xc:stock_alert:cfg, log in xc:stock_alert:log), never on a server. Copy the text from "Export / import settings" and paste it on another device to move your rules (the alert log and rule states are not included).

For information only, not investment advice. Alerts are judged on delayed quotes and may not arrive depending on your browser or network.