diff --git a/import/asana/importAsana.ts b/import/asana/importAsana.ts
index 38c3e3e4b..19d119af7 100644
--- a/import/asana/importAsana.ts
+++ b/import/asana/importAsana.ts
@@ -3,7 +3,7 @@
 import * as fs from 'fs'
 import minimist from 'minimist'
 import {exit} from 'process'
-import {IArchive} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../../webapp/src/blocks/archive'
 import {IBlock} from '../../webapp/src/blocks/block'
 import {IPropertyOption, IPropertyTemplate, MutableBoard} from '../../webapp/src/blocks/board'
 import {MutableBoardView} from '../../webapp/src/blocks/boardView'
@@ -49,10 +49,11 @@ function main() {
     const input = JSON.parse(inputData) as Asana
 
     // Convert
-    const output = convert(input)
+    const blocks = convert(input)
 
     // Save output
-    const outputData = JSON.stringify(output)
+    // TODO: Stream output
+    const outputData = ArchiveUtils.buildBlockArchive(blocks)
     fs.writeFileSync(outputFile, outputData)
 
     console.log(`Exported to ${outputFile}`)
@@ -87,17 +88,11 @@ function getSections(input: Asana, projectId: string): Workspace[] {
     return [...sectionMap.values()]
 }
 
-function convert(input: Asana): IArchive {
-    const archive: IArchive = {
-        version: 1,
-        date: Date.now(),
-        blocks: []
-    }
-
+function convert(input: Asana): IBlock[] {
     const projects = getProjects(input)
     if (projects.length < 1) {
         console.error('No projects found')
-        return archive
+        return []
     }
 
     // TODO: Handle multiple projects
@@ -181,12 +176,10 @@ function convert(input: Asana): IArchive {
         }
     })
 
-    archive.blocks = blocks
-
     console.log('')
     console.log(`Found ${input.data.length} card(s).`)
 
-    return archive
+    return blocks
 }
 
 function showHelp() {
diff --git a/import/asana/package.json b/import/asana/package.json
index d29ed69f2..a8fc76ba6 100644
--- a/import/asana/package.json
+++ b/import/asana/package.json
@@ -7,8 +7,8 @@
   "scripts": {
     "lint": "eslint --ext .tsx,.ts . --quiet --cache",
 	"fix": "eslint --ext .tsx,.ts . --quiet --fix --cache",
-    "test": "ts-node importAsana.ts -i test/asana.json -o test/archive.focalboard",
-    "debug:test": "node --inspect=5858 -r ts-node/register importAsana.ts -i test/asana.json -o test/archive.focalboard"
+    "test": "ts-node importAsana.ts -i test/asana.json -o test/asana-import.focalboard",
+    "debug:test": "node --inspect=5858 -r ts-node/register importAsana.ts -i test/asana.json -o test/asana-import.focalboard"
   },
   "keywords": [],
   "author": "",
diff --git a/import/notion/importNotion.ts b/import/notion/importNotion.ts
index fdd1ad743..7b6512964 100644
--- a/import/notion/importNotion.ts
+++ b/import/notion/importNotion.ts
@@ -3,7 +3,7 @@ import * as fs from 'fs'
 import minimist from 'minimist'
 import path from 'path'
 import {exit} from 'process'
-import {IArchive} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../../webapp/src/blocks/archive'
 import {IBlock} from '../../webapp/src/blocks/block'
 import {IPropertyTemplate, MutableBoard} from '../../webapp/src/blocks/board'
 import {MutableBoardView} from '../../webapp/src/blocks/boardView'
@@ -70,10 +70,11 @@ async function main() {
     markdownFolder = path.join(inputFolder, basename)
 
     // Convert
-    const output = convert(input, title)
+    const blocks = convert(input, title)
 
     // Save output
-    const outputData = JSON.stringify(output)
+    // TODO: Stream output
+    const outputData = ArchiveUtils.buildBlockArchive(blocks)
     fs.writeFileSync(outputFile, outputData)
 
     console.log(`Exported to ${outputFile}`)
@@ -115,15 +116,9 @@ function getColumns(input: any[]) {
     return keys.slice(1)
 }
 
-function convert(input: any[], title: string): IArchive {
+function convert(input: any[], title: string): IBlock[] {
     const blocks: IBlock[] = []
 
-    const archive: IArchive = {
-        version: 1,
-        date: Date.now(),
-        blocks
-    }
-
     // Board
     const board = new MutableBoard()
     console.log(`Board: ${title}`)
@@ -160,7 +155,7 @@ function convert(input: any[], title: string): IArchive {
         console.log(keys)
         if (keys.length < 1) {
             console.error(`Expected at least one column`)
-            return archive
+            return blocks
         }
 
         const titleKey = keys[0]
@@ -216,7 +211,7 @@ function convert(input: any[], title: string): IArchive {
     console.log('')
     console.log(`Found ${input.length} card(s).`)
 
-    return archive
+    return blocks
 }
 
 function showHelp() {
diff --git a/import/notion/package.json b/import/notion/package.json
index f5d485dc2..6dfc1a83c 100644
--- a/import/notion/package.json
+++ b/import/notion/package.json
@@ -7,8 +7,8 @@
   "scripts": {
 	"lint": "eslint --ext .tsx,.ts . --quiet --cache",
 	"fix": "eslint --ext .tsx,.ts . --quiet --fix --cache",
-	"test": "ts-node importNotion.ts -i test/export -o test/archive.focalboard",
-    "debug:test": "node --inspect=5858 -r ts-node/register importNotion.ts -i test/export -o test/archive.focalboard"
+	"test": "ts-node importNotion.ts -i test/export -o test/notion-import.focalboard",
+    "debug:test": "node --inspect=5858 -r ts-node/register importNotion.ts -i test/export -o test/notion-import.focalboard"
   },
   "keywords": [],
   "author": "",
diff --git a/import/trello/importTrello.ts b/import/trello/importTrello.ts
index 96d1f3f77..07bcf0077 100644
--- a/import/trello/importTrello.ts
+++ b/import/trello/importTrello.ts
@@ -3,7 +3,7 @@
 import * as fs from 'fs'
 import minimist from 'minimist'
 import {exit} from 'process'
-import {IArchive} from '../../webapp/src/blocks/archive'
+import {ArchiveUtils} from '../../webapp/src/blocks/archive'
 import {IBlock} from '../../webapp/src/blocks/block'
 import {IPropertyOption, IPropertyTemplate, MutableBoard} from '../../webapp/src/blocks/board'
 import {MutableBoardView} from '../../webapp/src/blocks/boardView'
@@ -49,16 +49,17 @@ function main() {
     const input = JSON.parse(inputData) as Trello
 
     // Convert
-    const output = convert(input)
+    const blocks = convert(input)
 
     // Save output
-    const outputData = JSON.stringify(output)
+    // TODO: Stream output
+    const outputData = ArchiveUtils.buildBlockArchive(blocks)
     fs.writeFileSync(outputFile, outputData)
 
     console.log(`Exported to ${outputFile}`)
 }
 
-function convert(input: Trello): IArchive {
+function convert(input: Trello): IBlock[] {
     const blocks: IBlock[] = []
 
     // Board
@@ -136,16 +137,10 @@ function convert(input: Trello): IArchive {
         }
     })
 
-    const archive: IArchive = {
-        version: 1,
-        date: Date.now(),
-        blocks
-    }
-
     console.log('')
     console.log(`Found ${input.cards.length} card(s).`)
 
-    return archive
+    return blocks
 }
 
 function showHelp() {
diff --git a/import/trello/package.json b/import/trello/package.json
index 6cc1eba08..27cec842e 100644
--- a/import/trello/package.json
+++ b/import/trello/package.json
@@ -7,8 +7,8 @@
   "scripts": {
 	"lint": "eslint --ext .tsx,.ts . --quiet --cache",
 	"fix": "eslint --ext .tsx,.ts . --quiet --fix --cache",
-    "test": "ts-node importTrello.ts -i test/trello.json -o test/archive.focalboard",
-    "debug:test": "node --inspect=5858 -r ts-node/register importTrello.ts -i test/trello.json -o test/archive.focalboard"
+    "test": "ts-node importTrello.ts -i test/trello.json -o test/trello-import.focalboard",
+    "debug:test": "node --inspect=5858 -r ts-node/register importTrello.ts -i test/trello.json -o test/trello-import.focalboard"
   },
   "keywords": [],
   "author": "",
diff --git a/webapp/src/archiver.ts b/webapp/src/archiver.ts
index c4d9aed28..dd459d401 100644
--- a/webapp/src/archiver.ts
+++ b/webapp/src/archiver.ts
@@ -1,7 +1,8 @@
 // Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
 // See LICENSE.txt for license information.
-import {IArchive} from './blocks/archive'
-import {IMutableBlock} from './blocks/block'
+import {ArchiveUtils, IArchiveHeader, IArchiveLine, IBlockArchiveLine} from './blocks/archive'
+import {IBlock} from './blocks/block'
+import {LineReader} from './lineReader'
 import mutator from './mutator'
 import {Utils} from './utils'
 import {BoardTree} from './viewModel/boardTree'
@@ -9,28 +10,16 @@ import {BoardTree} from './viewModel/boardTree'
 class Archiver {
     static async exportBoardTree(boardTree: BoardTree): Promise<void> {
         const blocks = boardTree.allBlocks
-        const archive: IArchive = {
-            version: 1,
-            date: Date.now(),
-            blocks,
-        }
-
-        this.exportArchive(archive)
+        this.exportArchive(blocks)
     }
 
     static async exportFullArchive(): Promise<void> {
         const blocks = await mutator.exportFullArchive()
-        const archive: IArchive = {
-            version: 1,
-            date: Date.now(),
-            blocks,
-        }
-
-        this.exportArchive(archive)
+        this.exportArchive(blocks)
     }
 
-    private static exportArchive(archive: IArchive): void {
-        const content = JSON.stringify(archive)
+    private static exportArchive(blocks: readonly IBlock[]): void {
+        const content = ArchiveUtils.buildBlockArchive(blocks)
 
         const date = new Date()
         const filename = `archive-${date.getFullYear()}-${date.getMonth() + 1}-${date.getDate()}.focalboard`
@@ -48,32 +37,76 @@ class Archiver {
         // TODO: Remove or reuse link
     }
 
+    private static async importBlocksFromFile(file: File): Promise<void> {
+        let blockCount = 0
+        const maxBlocksPerImport = 1000
+        let blocks: IBlock[] = []
+
+        let isFirstLine = true
+        return new Promise<void>((resolve) => {
+            LineReader.readFile(file, async (line, completed) => {
+                if (completed) {
+                    if (blocks.length > 0) {
+                        await mutator.importFullArchive(blocks)
+                        blockCount += blocks.length
+                    }
+                    Utils.log(`Imported ${blockCount} blocks.`)
+                    resolve()
+                    return
+                }
+
+                if (isFirstLine) {
+                    isFirstLine = false
+                    const header = JSON.parse(line) as IArchiveHeader
+                    if (header.date && header.version >= 1) {
+                        const date = new Date(header.date)
+                        Utils.log(`Import archive, version: ${header.version}, date/time: ${date.toLocaleString()}.`)
+                    }
+                } else {
+                    const row = JSON.parse(line) as IArchiveLine
+                    if (!row || !row.type || !row.data) {
+                        Utils.logError('importFullArchive ERROR parsing line')
+                        return
+                    }
+                    switch (row.type) {
+                    case 'block': {
+                        const blockLine = row as IBlockArchiveLine
+                        const block = blockLine.data
+                        if (Archiver.isValidBlock(block)) {
+                            blocks.push(block)
+                            if (blocks.length >= maxBlocksPerImport) {
+                                const blocksToSend = blocks
+                                blocks = []
+                                await mutator.importFullArchive(blocksToSend)
+                                blockCount += blocksToSend.length
+                            }
+                        }
+                        break
+                    }
+                    }
+                }
+            })
+        })
+    }
+
+    static isValidBlock(block: IBlock): boolean {
+        if (!block.id || !block.rootId) {
+            return false
+        }
+
+        return true
+    }
+
     static importFullArchive(onComplete?: () => void): void {
         const input = document.createElement('input')
         input.type = 'file'
         input.accept = '.focalboard'
         input.onchange = async () => {
             const file = input.files && input.files[0]
-            const contents = await (new Response(file)).text()
-            Utils.log(`Import ${contents.length} bytes.`)
-            const archive: IArchive = JSON.parse(contents)
-            const {blocks} = archive
-            const date = new Date(archive.date)
-            Utils.log(`Import archive, version: ${archive.version}, date/time: ${date.toLocaleString()}, ${blocks.length} block(s).`)
+            if (file) {
+                await Archiver.importBlocksFromFile(file)
+            }
 
-            // Basic error checking
-            let filteredBlocks = blocks.filter((o) => Boolean(o.id))
-
-            Utils.log(`Import ${filteredBlocks.length} filtered blocks with ids.`)
-
-            this.fixRootIds(filteredBlocks)
-
-            filteredBlocks = filteredBlocks.filter((o) => Boolean(o.rootId))
-
-            Utils.log(`Import ${filteredBlocks.length} filtered blocks with rootIds.`)
-
-            await mutator.importFullArchive(filteredBlocks)
-            Utils.log('Import completed')
             onComplete?.()
         }
 
@@ -83,42 +116,6 @@ class Archiver {
 
         // TODO: Remove or reuse input
     }
-
-    private static fixRootIds(blocks: IMutableBlock[]) {
-        const blockMap = new Map(blocks.map((o) => [o.id, o]))
-        const maxLevels = 5
-        for (let i = 0; i < maxLevels; i++) {
-            let missingRootIds = false
-            blocks.forEach((o) => {
-                if (o.parentId) {
-                    const parent = blockMap.get(o.parentId)
-                    if (parent) {
-                        o.rootId = parent.rootId
-                    } else {
-                        Utils.assert(`No parent for ${o.type}: ${o.id} (${o.title})`)
-                    }
-                    if (!o.rootId) {
-                        missingRootIds = true
-                    }
-                } else {
-                    o.rootId = o.id
-                }
-            })
-
-            if (!missingRootIds) {
-                Utils.log(`fixRootIds in ${i} levels`)
-                break
-            }
-        }
-
-        // Check and log remaining errors
-        blocks.forEach((o) => {
-            if (!o.rootId) {
-                const parent = blockMap.get(o.parentId)
-                Utils.logError(`RootId is null: ${o.type} ${o.id}, parentId ${o.parentId}: ${o.title}, parent: ${parent?.type}, parent.rootId: ${parent?.rootId}, parent.title: ${parent?.title}`)
-            }
-        })
-    }
 }
 
 export {Archiver}
diff --git a/webapp/src/blocks/archive.test.ts b/webapp/src/blocks/archive.test.ts
new file mode 100644
index 000000000..f4270056e
--- /dev/null
+++ b/webapp/src/blocks/archive.test.ts
@@ -0,0 +1,24 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+import {TestBlockFactory} from '../test/testBlockFactory'
+
+import {ArchiveUtils} from './archive'
+import {IBlock} from './block'
+
+test('archive: archive and unarchive', async () => {
+    const blocks: IBlock[] = []
+
+    const board = TestBlockFactory.createBoard()
+    blocks.push(board)
+    blocks.push(TestBlockFactory.createBoardView(board))
+    const card = TestBlockFactory.createCard(board)
+    blocks.push(card)
+    blocks.push(TestBlockFactory.createText(card))
+    blocks.push(TestBlockFactory.createDivider(card))
+    blocks.push(TestBlockFactory.createImage(card))
+
+    const archive = ArchiveUtils.buildBlockArchive(blocks)
+    const unarchivedBlocks = ArchiveUtils.parseBlockArchive(archive)
+
+    expect(unarchivedBlocks).toEqual(blocks)
+})
diff --git a/webapp/src/blocks/archive.ts b/webapp/src/blocks/archive.ts
index 1a1b08a55..8dd420bdc 100644
--- a/webapp/src/blocks/archive.ts
+++ b/webapp/src/blocks/archive.ts
@@ -2,10 +2,80 @@
 // See LICENSE.txt for license information.
 import {IBlock} from './block'
 
-interface IArchive {
+interface IArchiveHeader {
     version: number
     date: number
-    blocks: readonly IBlock[]
 }
 
-export {IArchive}
+interface IArchiveLine {
+    type: string,
+    data: any,
+}
+
+// This schema allows the expansion of additional line types in the future
+interface IBlockArchiveLine extends IArchiveLine {
+    type: 'block',
+    data: IBlock
+}
+
+class ArchiveUtils {
+    static buildBlockArchive(blocks: readonly IBlock[]): string {
+        const header: IArchiveHeader = {
+            version: 1,
+            date: Date.now(),
+        }
+
+        const headerString = JSON.stringify(header)
+        let content = headerString + '\n'
+        for (const block of blocks) {
+            const line: IBlockArchiveLine = {
+                type: 'block',
+                data: block,
+            }
+            const lineString = JSON.stringify(line)
+            content += lineString
+            content += '\n'
+        }
+
+        return content
+    }
+
+    static parseBlockArchive(contents: string): IBlock[] {
+        const blocks: IBlock[] = []
+        const allLineStrings = contents.split('\n')
+        if (allLineStrings.length >= 2) {
+            const headerString = allLineStrings[0]
+            const header = JSON.parse(headerString) as IArchiveHeader
+            if (header.date && header.version >= 1) {
+                const lineStrings = allLineStrings.slice(1)
+                let lineNum = 2
+                for (const lineString of lineStrings) {
+                    if (!lineString) {
+                        // Ignore empty lines, e.g. last line
+                        continue
+                    }
+                    const line = JSON.parse(lineString) as IArchiveLine
+                    if (!line || !line.type || !line.data) {
+                        throw new Error(`ERROR parsing line ${lineNum}`)
+                    }
+                    switch (line.type) {
+                    case 'block': {
+                        const blockLine = line as IBlockArchiveLine
+                        const block = blockLine.data
+                        blocks.push(block)
+                        break
+                    }
+                    }
+
+                    lineNum += 1
+                }
+            } else {
+                throw new Error('ERROR parsing header')
+            }
+        }
+
+        return blocks
+    }
+}
+
+export {IArchiveHeader, IArchiveLine, IBlockArchiveLine, ArchiveUtils}
diff --git a/webapp/src/lineReader.ts b/webapp/src/lineReader.ts
new file mode 100644
index 000000000..e2cc06bbf
--- /dev/null
+++ b/webapp/src/lineReader.ts
@@ -0,0 +1,77 @@
+// Copyright (c) 2015-present Mattermost, Inc. All Rights Reserved.
+// See LICENSE.txt for license information.
+
+class LineReader {
+    private static appendBuffer(buffer1: Uint8Array, buffer2: Uint8Array): Uint8Array {
+        const tmp = new Uint8Array(buffer1.byteLength + buffer2.byteLength)
+        tmp.set(buffer1, 0)
+        tmp.set(buffer2, buffer1.byteLength)
+
+        return tmp
+    }
+
+    private static arrayBufferIndexOf(buffer: Uint8Array, charCode: number): number {
+        for (let i = 0; i < buffer.byteLength; ++i) {
+            if (buffer[i] === charCode) {
+                return i
+            }
+        }
+
+        return -1
+    }
+
+    static readFile(file: File, callback: (line: string, completed: boolean) => Promise<void>): void {
+        let buffer = new Uint8Array(0)
+
+        const chunkSize = 1024 * 1000
+        let offset = 0
+        const fr = new FileReader()
+        const decoder = new TextDecoder()
+
+        fr.onload = async () => {
+            const chunk = new Uint8Array(fr.result as ArrayBuffer)
+            buffer = LineReader.appendBuffer(buffer, chunk)
+
+            const newlineChar = 10 // '\n'
+            let newlineIndex = LineReader.arrayBufferIndexOf(buffer, newlineChar)
+            while (newlineIndex >= 0) {
+                const result = decoder.decode(buffer.slice(0, newlineIndex))
+                buffer = buffer.slice(newlineIndex + 1)
+
+                // eslint-disable-next-line no-await-in-loop
+                await callback(result, false)
+                newlineIndex = LineReader.arrayBufferIndexOf(buffer, newlineChar)
+            }
+
+            offset += chunkSize
+            if (offset >= file.size) {
+                // Completed
+
+                if (buffer.byteLength > 0) {
+                    // Handle last line
+                    await callback(decoder.decode(buffer), false)
+                }
+
+                await callback('', true)
+                return
+            }
+
+            seek()
+        }
+
+        fr.onerror = () => {
+            callback('', true)
+        }
+
+        seek()
+
+        function seek() {
+            const slice = file.slice(offset, offset + chunkSize)
+
+            // Need to read as an ArrayBuffer (instead of text) to handle unicode boundaries
+            fr.readAsArrayBuffer(slice)
+        }
+    }
+}
+
+export {LineReader}
diff --git a/webapp/src/octoClient.ts b/webapp/src/octoClient.ts
index cebfb5daa..e35b66ba8 100644
--- a/webapp/src/octoClient.ts
+++ b/webapp/src/octoClient.ts
@@ -138,9 +138,10 @@ class OctoClient {
 
     async importFullArchive(blocks: readonly IBlock[]): Promise<Response> {
         Utils.log(`importFullArchive: ${blocks.length} blocks(s)`)
-        blocks.forEach((block) => {
-            Utils.log(`\t ${block.type}, ${block.id}`)
-        })
+
+        // blocks.forEach((block) => {
+        //     Utils.log(`\t ${block.type}, ${block.id}`)
+        // })
         const body = JSON.stringify(blocks)
         return fetch(this.serverUrl + '/api/v1/blocks/import', {
             method: 'POST',
diff --git a/webapp/src/octoListener.ts b/webapp/src/octoListener.ts
index 175a2d799..898eb03b4 100644
--- a/webapp/src/octoListener.ts
+++ b/webapp/src/octoListener.ts
@@ -108,7 +108,6 @@ class OctoListener {
 
                 switch (message.action) {
                 case 'UPDATE_BLOCK':
-                    Utils.log(`OctoListener update block: ${message.block?.id}`)
                     this.queueUpdateNotification(message.block!)
                     break
                 default:
@@ -207,6 +206,9 @@ class OctoListener {
     }
 
     private flushUpdateNotifications() {
+        for (const block of this.updatedBlocks) {
+            Utils.log(`OctoListener flush update block: ${block.id}`)
+        }
         this.onChange?.(this.updatedBlocks)
         this.updatedBlocks = []
     }