Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2026	Mar. 31, 2025
Cash flows from operating activities
Net income	$ 203,981	$ 26,158
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization	4,210	3,963
Non-cash operating lease cost	1,676	1,468
Amortization of premium (accretion of discount) on marketable securities, net	(4,297)	(8,884)
Stock-based compensation expense	68,336	85,414
Other adjustments	(691)	(138)
Changes in operating assets and liabilities:
Accounts receivable	67,957	23,359
Prepaid expenses and other assets	(23,752)	(17,006)
Operating lease right-of-use assets and liabilities	(1,815)	(1,780)
Accounts payable	(10,983)	(1,046)
Accrued expenses and other liabilities	7,631	16,070
Net cash provided by (used in) operating activities	312,253	127,578
Cash flows from investing activities
Purchases of property and equipment	(1,090)	(979)
Purchases of marketable securities	(364,929)	(504,846)
Maturities of marketable securities	474,468	465,062
Proceeds from sale of marketable securities	17,989	12,372
Other investing activities	(1,616)	889
Net cash provided by (used in) investing activities	124,822	(27,502)
Cash flows from financing activities
Proceeds from exercise of employee stock options	4,899	10,184
Taxes paid related to net share settlement of restricted stock units	(16,196)	(36,675)
Repurchases of Class A common stock	(4,999)	0
Net cash provided by (used in) financing activities	(16,296)	(26,491)
Net increase (decrease) in cash and cash equivalents	420,779	73,585
Cash and cash equivalents at the beginning of the period	953,569	562,142
Cash and cash equivalents at the end of the period	$ 1,374,348	$ 635,727

Increase (Decrease) In Operating Lease Asset And Liability

No definition available.

Name:	rddt_IncreaseDecreaseInOperatingLeaseAssetAndLiability
Namespace Prefix:	rddt_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.