{"id":78444,"date":"2026-03-31T10:06:24","date_gmt":"2026-03-31T04:36:24","guid":{"rendered":"https:\/\/www.tothenew.com\/blog\/?p=78444"},"modified":"2026-04-06T10:55:06","modified_gmt":"2026-04-06T05:25:06","slug":"hermes-v1-by-default-in-react-native-0-84-the-biggest-performance-win-of-2026","status":"publish","type":"post","link":"https:\/\/www.tothenew.com\/blog\/hermes-v1-by-default-in-react-native-0-84-the-biggest-performance-win-of-2026\/","title":{"rendered":"Hermes V1 by Default in React Native 0.84: The Biggest Performance Win of 2026"},"content":{"rendered":"<h1><strong>Introduction<\/strong><\/h1>\n<p>If you haven\u2019t upgraded to React Native 0.84 yet, you\u2019re literally leaving free performance on the table.<\/p>\n<p>In early 2026, the React Native team released version 0.84 and has made Hermes V1 <strong>the default JavaScript engine for both iOS and Android<\/strong>. No config changes required. No migration steps. Just npx react-native upgrade (or create a new project) and you instantly get:<\/p>\n<ul>\n<li>Faster JavaScript execution<\/li>\n<li>Lower memory footprint<\/li>\n<li>Smoother 60 fps animations &amp; lists<\/li>\n<li>Faster cold starts<\/li>\n<\/ul>\n<p>This is the single biggest \u201cset it and forget it\u201d improvement React Native has shipped since the New Architecture became default in 0.82.<\/p>\n<p>In this post we\u2019ll look at why Hermes V1 matters so much in 2026, how to verify it\u2019s active in your app, a real-world code example that shows the performance difference clearly, and what to expect when measuring it.<\/p>\n<h2>1. What changed in React Native 0.84?<\/h2>\n<p>Hermes has been the default engine since 0.70, but Hermes V1 (released in stages during 2025 and stabilized in 0.84) brings a rewritten compiler, new bytecode format, improved JIT, concurrent garbage collection (Hades), and better handling of modern JavaScript patterns used by React 19+.<\/p>\n<p>Real-world numbers reported by teams after upgrading to 0.84 (Hermes V1 default):<\/p>\n<ul>\n<li>25\u201355% faster JS execution in heavy components<\/li>\n<li>15\u201340% lower memory footprint<\/li>\n<li>10\u201330% faster cold start time (especially noticeable on low-end Android devices)<\/li>\n<li>Significantly reduced jank\/lag during typing + filtering + sorting operations<\/li>\n<\/ul>\n<p>And again: no code changes required.<\/p>\n<h2>2. How to confirm Hermes V1 is running<\/h2>\n<p>Drop this snippet anywhere in your app (e.g. in useEffect in App.js):<\/p>\n<div id=\"attachment_78446\" style=\"width: 635px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-78446\" decoding=\"async\" loading=\"lazy\" class=\"wp-image-78446 size-large\" src=\"https:\/\/www.tothenew.com\/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-1024x696.png\" alt=\"Checking Hermes\" width=\"625\" height=\"425\" srcset=\"\/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-1024x696.png 1024w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-300x204.png 300w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-768x522.png 768w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-1536x1044.png 1536w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-2048x1392.png 2048w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/checkingHermes-1-624x424.png 624w\" sizes=\"(max-width: 625px) 100vw, 625px\" \/><p id=\"caption-attachment-78446\" class=\"wp-caption-text\">Checking Hermes<\/p><\/div>\n<p><strong>Typical Output on 0.84+ &#8212;-<\/strong><\/p>\n<p>Hermes active \u2014 OSS Release Version: 250829098.0.9<br \/>\nLikely Hermes V1? YES<\/p>\n<h2>3. Practical example: Heavy Searchable List<\/h2>\n<p>This component simulates a real e-commerce \/ analytics screen: 5,000 items, live filtering + sorting + calculations on every keystroke.<\/p>\n<div id=\"attachment_78526\" style=\"width: 803px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-78526\" decoding=\"async\" loading=\"lazy\" class=\" wp-image-78526\" src=\"https:\/\/www.tothenew.com\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-1024x640.png\" alt=\"Heavy Computation\" width=\"793\" height=\"496\" srcset=\"\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-1024x640.png 1024w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-300x188.png 300w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-768x480.png 768w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-1536x960.png 1536w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-2048x1280.png 2048w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.03\u202fPM-624x390.png 624w\" sizes=\"(max-width: 793px) 100vw, 793px\" \/><p id=\"caption-attachment-78526\" class=\"wp-caption-text\">Heavy Computation<\/p><\/div>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"alignnone wp-image-78527\" src=\"https:\/\/www.tothenew.com\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM.png\" alt=\"\" width=\"818\" height=\"511\" srcset=\"\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM.png 3456w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM-300x188.png 300w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM-1024x640.png 1024w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM-768x480.png 768w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM-1536x960.png 1536w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM-2048x1280.png 2048w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-16-at-3.31.16\u202fPM-624x390.png 624w\" sizes=\"(max-width: 818px) 100vw, 818px\" \/><\/p>\n<p><strong>Typical timings observed in 2026 (RN 0.84, Hermes V1 default):<\/strong><\/p>\n<p>Debug: 2\u201315 ms per keystroke (very smooth)<br \/>\nRelease: often 1\u20138 ms<br \/>\nOlder Hermes or JSC: frequently 50\u2013250 ms \u2192 visible typing lag<\/p>\n<div id=\"attachment_78461\" style=\"width: 620px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-78461\" decoding=\"async\" loading=\"lazy\" class=\" wp-image-78461\" src=\"https:\/\/www.tothenew.com\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM.png\" alt=\"Search Execution Time\" width=\"610\" height=\"1136\" srcset=\"\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM.png 960w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM-161x300.png 161w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM-550x1024.png 550w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM-768x1430.png 768w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM-825x1536.png 825w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.08\u202fAM-624x1162.png 624w\" sizes=\"(max-width: 610px) 100vw, 610px\" \/><p id=\"caption-attachment-78461\" class=\"wp-caption-text\">Search Execution Time<\/p><\/div>\n<p><img decoding=\"async\" loading=\"lazy\" class=\"alignnone wp-image-78462\" src=\"https:\/\/www.tothenew.com\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM.png\" alt=\"\" width=\"635\" height=\"403\" srcset=\"\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM.png 2536w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM-300x190.png 300w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM-1024x649.png 1024w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM-768x487.png 768w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM-1536x974.png 1536w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM-2048x1299.png 2048w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-10.39.11\u202fAM-624x396.png 624w\" sizes=\"(max-width: 635px) 100vw, 635px\" \/><\/p>\n<h2>4. Measuring with the new React Native DevTools<\/h2>\n<p>Open DevTools (bundled since 0.84), go to Performance tab, record while typing and scrolling. You\u2019ll see dramatically shorter JS execution bars compared to older versions.<\/p>\n<div id=\"attachment_78464\" style=\"width: 955px\" class=\"wp-caption alignnone\"><img aria-describedby=\"caption-attachment-78464\" decoding=\"async\" loading=\"lazy\" class=\" wp-image-78464\" src=\"https:\/\/www.tothenew.com\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM.png\" alt=\"JS Execution Bars\" width=\"945\" height=\"611\" srcset=\"\/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM.png 2624w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM-300x194.png 300w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM-1024x662.png 1024w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM-768x496.png 768w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM-1536x993.png 1536w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM-2048x1324.png 2048w, \/blog\/wp-ttn-blog\/uploads\/2026\/03\/Screenshot-2026-03-15-at-1.27.39\u202fPM-624x403.png 624w\" sizes=\"(max-width: 945px) 100vw, 945px\" \/><p id=\"caption-attachment-78464\" class=\"wp-caption-text\">JS Execution Bars<\/p><\/div>\n<h1>Conclusion<\/h1>\n<p>React Native 0.84 with Hermes V1 default is one of those rare upgrades where you literally get better performance for free \u2014 no migration pain, no new architecture headaches, no rewriting business logic.<\/p>\n<p>If your app involves any kind of dynamic lists, search-as-you-type, real-time calculations, or complex component trees, upgrading to 0.84 will almost certainly feel noticeably snappier \u2014 especially on mid-range Android devices.<\/p>\n<p>New project? \u2192 just use latest (npx react-native@latest init)<br \/>\nExisting app? \u2192 run npx react-native upgrade and measure<\/p>\n<p>Hermes V1 isn\u2019t flashy marketing \u2014 it\u2019s quiet, boring, excellent engineering that makes every user interaction a little faster.<\/p>\n<p>Thank You<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Introduction If you haven\u2019t upgraded to React Native 0.84 yet, you\u2019re literally leaving free performance on the table. In early 2026, the React Native team released version 0.84 and has made Hermes V1 the default JavaScript engine for both iOS and Android. No config changes required. No migration steps. Just npx react-native upgrade (or create [&hellip;]<\/p>\n","protected":false},"author":2117,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"iawp_total_views":9},"categories":[5881],"tags":[8481,8483,2683,5853,6078],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts\/78444"}],"collection":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/users\/2117"}],"replies":[{"embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/comments?post=78444"}],"version-history":[{"count":6,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts\/78444\/revisions"}],"predecessor-version":[{"id":79430,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/posts\/78444\/revisions\/79430"}],"wp:attachment":[{"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/media?parent=78444"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/categories?post=78444"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.tothenew.com\/blog\/wp-json\/wp\/v2\/tags?post=78444"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}