Is it halal to invest in the stock market, and how do I screen for halal stocks?

Yes, investing in the stock market can be halal, but not automatically — it requires screening each stock on two levels: first, the company's core business must not be primarily in a prohibited sector (conventional banking/insurance, alcohol, gambling, pork, adult entertainment, and similar); second, because almost no modern listed company is entirely free of interest-based debt or interest income, most contemporary Shariah boards apply financial ratio thresholds (commonly, interest-bearing debt and interest-bearing cash/securities each kept under roughly 30–33% of market capitalization) to decide what's tolerable.

Where genuine scholarly difference exists is in the exact ratio cutoffs and methodology — AAOIFI's standard, and the slightly different approaches used by different Shariah screening services (Zoya, Musaffa, Islamicly are commonly used apps/platforms for this), don't always agree to the decimal point, so a stock can pass one screen and fail another. Even for stocks that pass screening, most scholars require "purification" — calculating and donating to charity the small percentage of the company's income that came from impermissible sources (like interest on its cash reserves), since that portion of your dividend or capital gain isn't considered clean even though the overall investment is permitted.

Source: general framework reflected in AAOIFI Shariah standards and contemporary Shariah stock-screening methodologies; see Musaffa Academy and Fiqh Council of North America guidance on halal stock screening.